Test Equipment Anonymous (TEA) group therapy thread

[Vince]

Tek RM17 repair update

- On ranges 20 / 2 / 0.2 and 20mV / DIV settings, it fails to display the square wave. Instead, it displays sharp negative and positive pulses. That is, the square wave is like going through an RC "differentiator"  circuit. a parasitic one of course ! Must be a simple fix I guess... broken connection, bad contact somewhere...
Since it affects only all the 20/2 etc ranges, the problem must be localized to a decade selector, hence should be able to narrow it down quite a bit in the schematic, I would think.

Worked on that issue above.

So I looked at the attenuator schematic, at the x2 section, and wondered what failure mode could potentially turn it into an RC differentiator, which would explain the issue at hand. Looked to me that yes there was a way for it to behave so, if resistor R132, the 500K one, upper leg of the voltage divider, was open circuit. So I checked that and bingo, that resistor was indeed open circuit. Replaced it, fired up the scope and... now the freaking scope won't display a trace at all ! Black screen....     Eventually noticed that there is ONE combination of calibrator amplitude, and attenuator setting, that DOES give me a trace : if I wayyyyy overdrive the input. Set the attenuator to its most sensitive range, 0.1V / DIV (below that, it's AC only and no trace on those no matter what), and set the calibrator output to 50 or 100Vpp, then all by magic I get a trace on the screen.

It's midnight and I am tired so I don't feel like elaborating.. but in short, I can't see how me replacing a freaking resistor in the attenuator, can cause the trace to disappear... and from the clues I gather, it looks like it's the vertical amplifier that's kaput, and likely one of the tubes that just died in front of me, causing a mega offset upwards, way off screen. I am too exhausted and pissed off, to look at that now. Tomorrow.

For now.... good night... 

[Specmaster]

Driver frozen up is a very common failure mode; I've replaced more than I can count. 

mnem
No rest for the wicked.

Yep, I've seen this kind of failure before, but always as a direct result of ripped cones which allow the voice coil to go off centre, water damaged, allowing the cone to stretch / move or as a direct result of overload burning the coil out and jamming in the air gap, but this one has none of these attributes, looking at it you'd swear it was good to go.

[Cubdriver]

After a few hours of cooking, a tweak of the oscillator adjustment cap has brought it within 10 Hz.





-Pat

[mnementh]

Driver frozen up is a very common failure mode; I've replaced more than I can count. 

mnem
No rest for the wicked.

Yep, I've seen this kind of failure before, but always as a direct result of ripped cones which allow the voice coil to go off centre, water damaged, allowing the cone to stretch / move or as a direct result of overload burning the coil out and jamming in the air gap, but this one has none of these attributes, looking at it you'd swear it was good to go.

Naaahhh... these things operate in a hostile environment: the inside of a door. This is a little solar oven, where temps can get high enough to melt plastics; on top of that, it collects water from the windows. Under the right circumstances, this can create a sauna inside that little tin can. Now multiply that by 10-15 years living outdoors and... 

The magnet assembly on these speakers (no matter what the frame is made of) will have ferrous metal on either side of the voice coil; in most cases it's only a matter of time before that begins to rust, no matter what it's plated with.

Seriously... a very common failure.

As for replacing all 4 drivers... no need to do that.  When you don't have an exact match for the original, you replace faulty speakers in a car in pairs. Why would you think it matters if they don't match front to back? Do you have any idea how many cars out there are made with 4-6" drivers in front and 6-8" or 6x9s in back?

Worst case scenario you have to slide the fader control forward a bit to balance the sound. Big fat hairy deal.

mnem
 

[Zucca]

I officially underestimate how dangerous lead is



I am now considering to get rid of the Pb solder wire that I sporadically using.
Maybe the low temp metcal tip are also the next one to go... still pondering what to do.

Even with proper air suction/filter I do not feel comfortable anymore...

EDIT: on the other hand

[Cubdriver]

I found the rubidium reference, and am letting things cook for a while.  It looks like the 5340A is pretty good, but the 5216A is about 50 Hz off.  I'm going to leave them running for a few hours then try tweaking it and getting it more accurate.



-Pat

Piles of TE like this one is a major driver in my gathering. You are a role model.

But, of course, now, that you've gotfound a Rb clock, wouldn't it be nice to let a GNSS receiver steer it?  For more vintage points, you could beat it towards WWV, of course, but I'm quite happy to accept USNO via space...

I did get a set of the Lucent GPSDO boxes at the same time I got the rubidium one - fall of 2017 - but never got around to setting them up.  I need to scare up the GPS antenna (bought one a while back, but like many things here it's in hiding somewhere here) and also need a bias tee as it's an amplified antenna.  Finally playing with these counters has piqued my interest again, so I think setting the GPSDO up has just risen on the priority list.





-Pat

[mnementh]

Strange how some things can languish in the "to do" queue...

This afternoon I printed up a adapter to go on a 120VAC pump for air mattresses, inflatable toys, etc that I have literally had as long as you've had those standards. Every time I needed the stoopit thing, I made do with something that I felt was less assache at the time. 

Imagining now how much assache I might have saved so many times over the last 5 years if I'd just fixed the damned thing and kept it handy in a toolbox... 

mnem
 

[med6753]

Tek RM17 repair update

- On ranges 20 / 2 / 0.2 and 20mV / DIV settings, it fails to display the square wave. Instead, it displays sharp negative and positive pulses. That is, the square wave is like going through an RC "differentiator"  circuit. a parasitic one of course ! Must be a simple fix I guess... broken connection, bad contact somewhere...
Since it affects only all the 20/2 etc ranges, the problem must be localized to a decade selector, hence should be able to narrow it down quite a bit in the schematic, I would think.

Worked on that issue above.

So I looked at the attenuator schematic, at the x2 section, and wondered what failure mode could potentially turn it into an RC differentiator, which would explain the issue at hand. Looked to me that yes there was a way for it to behave so, if resistor R132, the 500K one, upper leg of the voltage divider, was open circuit. So I checked that and bingo, that resistor was indeed open circuit. Replaced it, fired up the scope and... now the freaking scope won't display a trace at all ! Black screen....     Eventually noticed that there is ONE combination of calibrator amplitude, and attenuator setting, that DOES give me a trace : if I wayyyyy overdrive the input. Set the attenuator to its most sensitive range, 0.1V / DIV (below that, it's AC only and no trace on those no matter what), and set the calibrator output to 50 or 100Vpp, then all by magic I get a trace on the screen.

It's midnight and I am tired so I don't feel like elaborating.. but in short, I can't see how me replacing a freaking resistor in the attenuator, can cause the trace to disappear... and from the clues I gather, it looks like it's the vertical amplifier that's kaput, and likely one of the tubes that just died in front of me, causing a mega offset upwards, way off screen. I am too exhausted and pissed off, to look at that now. Tomorrow.

For now.... good night... 

Vince, I downloaded the Type 317 manual to look over the schematic in an attempt to give you some areas to check. But I don't have time tonight to really go into detail. I'll look it over in the morning and give some suggestions. I suspect your variable attenuator balance is way off.     

[GreyWoolfe]

Just like the last time you said this, I'm still making my breakfast tacos with Carb Balance Tortillas. 4 grams net carbs FTW. 

mnem
"It's kinda like  déjà vu... kinda like  déjà vu..."

I don't recall saying that once before. Maybe I did. The mind is a terrible thing to lose.

For the past few weeks I've been on basically a no carb keto diet. Recent trip to the primary dr and routine blood work shows that my current diabetic medication (Metformin) is no longer working. A1C has shot upwards. So decided to buckle down on the diet and also bought a monitor to check my blood sugar. Fasting blood sugar is typically averaging around 150. Should be 120 or less or ideally 100 or less. Can't raise the Metformin any higher. Alternatives were the very heavily advertised Januvia, Rybelsus, Ozempic, etc. I checked my drug plan and the co-pays for these drugs is ridiculous. Fuck the drug companies, not paying that. So my only alternative is to go on insulin which I accept as necessary. In discussions with dr now as to which insulin is appropriate. And the cost is reasonable under my drug plan. So it looks like my daily routine will now involve injecting myself. Getting old sucks. Oh well.     

Of all the things I've lost, it's my mind I miss the most.   Sorry for being snarky aboot it. 

Aww, man... that blows. Keto is hard to maintain; I really can only ever manage it for a few weeks at a time then a day or 3 off. Transitioning back into ketosis after is just the pits. 

For a while there in Canada I was managing to do both walkies with the kids 3x a week and an upper body dumbbell workout the other days widda boi; then I could make occasional guerrilla attacks on the diet... like one meal in 3 or 4 days with pasta, bread, and/or a slice of pie for dessert... and not lose the ketosis if I was really good the next few days. But this winter has beaten me up pretty hard and we're just now getting back to the dumbbell regimen. 

My wife, OTOH... her numbers are the best they've been in over a decade. This gig has her walking pretty much all day; she's lost as much as I have and not dieting at all, aside from very vague "not too much sugar" and "not too much starch" at any meal. She's expecting the doc to decrease her Metformin the next time she has a checkup.

My best advice is the same as bd139's... get walking, keep walking, and do as much of it as you can physically bear the pain and keep pushing against that wall.

I totally regret letting "packing and moving" be an excuse for getting out of the habit. Now I have to claw my way back into the habit... and it gets harder every. fucking. time.

What's your daily carb threshold? I've been doing a goal of 15grams/1500 calories, but lately have been backsliding more towards 20gr/1800 calories a day or two a week. Weighing every fucking thing that goes in your mouth is a unmitigated drag. 

mnem
 

Med, hate seeing you go down that road.  I was heading there myself, Mrs GreyWoolfe was convinced I was heading there also.  I was up to 1000 mg of Metformin, twice a day, Glipizide was next.  Her kicking my tail to join her on weight watchers was my saving grace.  For us, all it took was a change in eating habits.  Lean meats, lots of veg and fruits, beans and lentils(dried and done in the pressure cooker to our recipe) and almost no simple carbs.  mnem, we do enjoy the occasional Mission carb balance tortilla ourselves.  We have found quite acceptable substitutes; zoodles for pasta, Quest protein chips made with psyllium husk instead of flour replaced potato chips, chicken sausage instead of pork sausage.  We do some plant based protein alternatives.  My favorite is MorningStar Farms chorizo crumbles with my eggs and oat bran in the morning.  No fried/greasy food and no processed sugar and we read the labels on everything.  No fast food.  It took weeks to get used to healthy eating and I fought it every step of the way.  A year later, no measuring of food except the pasta sauce for zoodles.  We eat proper serving sizes and I try to eat 5 times a day, 3 meals and 2 snacks.  Just did blood work for hematology/oncology and fasting blood sugar was 100 and my primary care took me off metformin 2 months ago.  A1C from 7.9 to 5.1. Yes, I still monitor my blood sugar every day, once a day-that's all Medicare will pay for as I am not insulin dependent.  And, honestly, I am not exercising much, as the monthly chemotherapy shots keeps me in a constant state of serious fatigue( zero testosterone in my system) and at the end of the day it's hard to do much of anything.  Most days, it's enough getting through work.  Looking forward to November when I get my last shot.  Hopefully, I will be able to get my life back on track and not be so tired.  Still down 133 pounds as of this morning, 385 to 252.  Thankfully, we have each other to hold us accountable and to encourage.  She is down 75.  We are planning to go out to dinner tomorrow for our 17th anniversary.  I will probably have what I usually have when we do go out to dinner, which is very rare now.  A salad, dressing on the side, keep the bread/roll and topped with a grilled protein of some sort, no appetizers or dessert. I like going to places that have all you can eat salad bars.

We both tried multiple diets and failed at all of them, some spectacularly.  Changing our lifestyle and eating habits has corrected much.  Mrs GreyWoolfe has had irritable bowel syndrome with diarrhea, IBS/D for years.  Without the fat and sugar in our diet, she has had to add a fiber substitute so she doesn't become constipated.  It is great to shop at wally world for cheap pants/polo shirts for work since I shrink out of clothing every couple of months.  No more big and tall stores with their outrageous prices.  I would encourage you to try healthy eating, no diet for a couple of months before going on insulin.  Friends and family that have ended up on insulin have had the same side effect, sugar craving which is a huge no-no.  Best of luck, med.  Fight the good fight.

[Cubdriver]

Strange how some things can languish in the "to do" queue...

This afternoon I printed up a adapter to go on a 120VAC pump for air mattresses, inflatable toys, etc that I have literally had as long as you've had those standards. Every time I needed the stoopit thing, I made do with something that I felt was less assache at the time. 

Imagining now how much assache I might have saved so many times over the last 5 years if I'd just fixed the damned thing and kept it handy in a toolbox... 

mnem
 

It really is.  Time can certainly fly.  I fired up the rubidium standard right away as it is stand-alone, but needed an antenna and cable for the GPSDO.  By the time I got the antenna it was winter and too crummy outside to set it up, so it got put to the side.  Now years later the antenna is around here somewhere.  Need to excavate.

And of course nothing is so permanent as a temporary fix that works well enough.  I have some temporary pex lines in the basement that have been in place for probably six years now.  Need to do a bit of plumbing, but it works so it stays below the noise floor of things that must be done.

-Pat

[med6753]

Med, hate seeing you go down that road.  I was heading there myself, Mrs GreyWoolfe was convinced I was heading there also.  I was up to 1000 mg of Metformin, twice a day, Glipizide was next.  Her kicking my tail to join her on weight watchers was my saving grace.  For us, all it took was a change in eating habits.  Lean meats, lots of veg and fruits, beans and lentils(dried and done in the pressure cooker to our recipe) and almost no simple carbs.  mnem, we do enjoy the occasional Mission carb balance tortilla ourselves.  We have found quite acceptable substitutes; zoodles for pasta, Quest protein chips made with psyllium husk instead of flour replaced potato chips, chicken sausage instead of pork sausage.  We do some plant based protein alternatives.  My favorite is MorningStar Farms chorizo crumbles with my eggs and oat bran in the morning.  No fried/greasy food and no processed sugar and we read the labels on everything.  No fast food.  It took weeks to get used to healthy eating and I fought it every step of the way.  A year later, no measuring of food except the pasta sauce for zoodles.  We eat proper serving sizes and I try to eat 5 times a day, 3 meals and 2 snacks.  Just did blood work for hematology/oncology and fasting blood sugar was 100 and my primary care took me off metformin 2 months ago.  A1C from 7.9 to 5.1. Yes, I still monitor my blood sugar every day, once a day-that's all Medicare will pay for as I am not insulin dependent.  And, honestly, I am not exercising much, as the monthly chemotherapy shots keeps me in a constant state of serious fatigue( zero testosterone in my system) and at the end of the day it's hard to do much of anything.  Most days, it's enough getting through work.  Looking forward to November when I get my last shot.  Hopefully, I will be able to get my life back on track and not be so tired.  Still down 133 pounds as of this morning, 385 to 252.  Thankfully, we have each other to hold us accountable and to encourage.  She is down 75.  We are planning to go out to dinner tomorrow for our 17th anniversary.  I will probably have what I usually have when we do go out to dinner, which is very rare now.  A salad, dressing on the side, keep the bread/roll and topped with a grilled protein of some sort, no appetizers or dessert. I like going to places that have all you can eat salad bars.

We both tried multiple diets and failed at all of them, some spectacularly.  Changing our lifestyle and eating habits has corrected much.  Mrs GreyWoolfe has had irritable bowel syndrome with diarrhea, IBS/D for years.  Without the fat and sugar in our diet, she has had to add a fiber substitute so she doesn't become constipated.  It is great to shop at wally world for cheap pants/polo shirts for work since I shrink out of clothing every couple of months.  No more big and tall stores with their outrageous prices.  I would encourage you to try healthy eating, no diet for a couple of months before going on insulin.  Friends and family that have ended up on insulin have had the same side effect, sugar craving which is a huge no-no.  Best of luck, med.  Fight the good fight.

Thanks for the encouragement. Weight for me is not an issue. I'm only 7 pounds above my target weight of 170 - 175 pounds. Type 2 Diabetes runs in my family on my Mother's side. And I've been lucky enough to carry on the tradition. I knew sooner or later I was going to be insulin dependent no matter what I did with my diet or weight. But I will continue a very low carb routine to avoid large blood sugar spikes. And small portions to keep the weight off. When I was working I had no problem keeping the weight off. As soon as I retired 10 pounds suddenly got packed on. But now that I doubled down on the diet it's slowly coming back off.     

[mansaxel]

Driver frozen up is a very common failure mode; I've replaced more than I can count. 

That's when the recone kit comes out. Such things do exist. I've done more JBL 2220 and 2225 15" drivers than I can count. Although, for a simple 6" car woofer, not likely to find one. Aftermarket foam surrounds, though.  That is a thing.

Get a pair of cheap aftermarket 4Ω speakers the right size and replace both so the sound is the same. If that speaker measures 2Ω DCR, actual impedance will be a bit higher; more like 2.5-3Ω. Inversely, a 4Ω impedance speaker will usually measure 3-3.6Ω DCR.

2Ω might be a battered 4Ω too.  I've done a few in-door replacements, and there's one coming up soon here. What I usually do, is to go to used parts dealers and buy from scrapped cars. For a lot of non-wear items (and a good deal wear items too) this is a very convenient and cheap way to prolong the life of your car.  In Sweden, there's a common online database service for about 150 dealers where you can search on mfr part number and find who's got it. Very, very effective and convenient.

Under any circumstances, in most cases using a lower impedance speaker will do nothing except decrease max volume a bit and make the amp run a bit cooler.

Now, lowered impedance, if we for a while play "DC == AC" simplification game, means more current. More current usually means hotter transistors. The limiting factor for output power is rail voltage, which will set an output level at which clipping happens. In an ideal amplifier, half the load impedance means double current at a fixed max voltage, doubling the output power, and making the amp run hotter. Less than ideal amplifiers usually mean that the power supply can't supply enough current, or the transistors won't deal with the power levels, placing a limit on how low load impedance safely can be.

I'm quite bad at electronics, and I only have professional user experience of power amplifiers, but this is what I learnt during perhaps 20 years doing such things on and off.

So, how come you predict the amp will run cooler? And then we've not discussed any passive crossover point moving because the impedance is a part of the filter..

[Peter_O]

Keysight has sent a link to the new AN-90 "The Power Handbook", now focussing on PS applications.
https://www.keysight.com/zz/en/assets/3121-1101/application-notes/The-Power-Handbook.pdf

They mention the 'old An-90', focussing on PS design.
Does anybody know a source? 

[tggzzz]

I officially underestimate how dangerous lead is

EDIT: on the other hand

The safety section contains a classic! (And presumably the orange safety specs allow better visibility through clouds of vapourised flux)

[McBryce]

I officially underestimate how dangerous lead is



I am now considering to get rid of the Pb solder wire that I sporadically using.
Maybe the low temp metcal tip are also the next one to go... still pondering what to do.

Even with proper air suction/filter I do not feel comfortable anymore...

EDIT: on the other hand

Lead is only dangerous if you inhale or eat it. The fumes from soldering contains no lead. Leads boiling point is 1749°C which your iron is never going to get to. The only danger from lead soldering is if you have lead residue on your hands and you put your fingers in your mouth or eat a sandwich/handle food etc. If you wash your hands after soldering, there is no danger (for you) associated with using lead solder.

McBryce. 

[Robert763]

Tek RM17 repair update

- On ranges 20 / 2 / 0.2 and 20mV / DIV settings, it fails to display the square wave. Instead, it displays sharp negative and positive pulses. That is, the square wave is like going through an RC "differentiator"  circuit. a parasitic one of course ! Must be a simple fix I guess... broken connection, bad contact somewhere...
Since it affects only all the 20/2 etc ranges, the problem must be localized to a decade selector, hence should be able to narrow it down quite a bit in the schematic, I would think.

Worked on that issue above.

So I looked at the attenuator schematic, at the x2 section, and wondered what failure mode could potentially turn it into an RC differentiator, which would explain the issue at hand. Looked to me that yes there was a way for it to behave so, if resistor R132, the 500K one, upper leg of the voltage divider, was open circuit. So I checked that and bingo, that resistor was indeed open circuit. Replaced it, fired up the scope and... now the freaking scope won't display a trace at all ! Black screen....     Eventually noticed that there is ONE combination of calibrator amplitude, and attenuator setting, that DOES give me a trace : if I wayyyyy overdrive the input. Set the attenuator to its most sensitive range, 0.1V / DIV (below that, it's AC only and no trace on those no matter what), and set the calibrator output to 50 or 100Vpp, then all by magic I get a trace on the screen.

It's midnight and I am tired so I don't feel like elaborating.. but in short, I can't see how me replacing a freaking resistor in the attenuator, can cause the trace to disappear... and from the clues I gather, it looks like it's the vertical amplifier that's kaput, and likely one of the tubes that just died in front of me, causing a mega offset upwards, way off screen. I am too exhausted and pissed off, to look at that now. Tomorrow.

For now.... good night... 

Hi Vince,
It's most likely you have disturbed something else or there was a coincidental failure.
First thing is to lift one end of the new resistor and see if it goes bock to the original condition. If not, something else has happened. I it does go back to the same state there is something weird going on.

[Saskia]

the postman just rang. twice ...

Got a Keithley 2000 in the mail. Sender information plus serial number intakt. boots wo errors. Selftest gets to 400, then asks me to insert 4 wire short which I don't have. Last calibration was in 2010. Cosmetically it looks a shitload better than the 2700. Display ok, no covers missing.

cost was 155 Pesos incl postage

[med6753]

Vince, I looked over the schematic for the RM17 and it appears from your description that the vertical amp is out of balance. Here's what I recommend to check it:

Set Trigger to Auto and Preset. That should cause the sweep to free run.

No signal on vertical input. Short the input to the chassis.
DC coupling, 0.2v, variable to calibrated.
Set vertical position to mid-range.

Check pin 6 of both V244 and V254. DCV should be equal or nearly equal. A large difference between them will force trace off screen.
Check pin 2 and 7 of V233A/B. Again, DCV should be equal or nearly equal.
Check pin 1 of V183 and V203 for 0V. If pin 1 of V203 has any voltage then coupling capacitor C171 is leaky and the source of your imbalance.
If all those checks are OK then slowly adjust the variable attenuator balance control to bring the trace on screen. Check that pin 6 of V244 and V254 become more or less equal. If they are and you still have no trace then make sure the sweep is free running.   

Edit......Last statement is incorrect. Should read: If there is a large difference in voltage yet V183 and V203 are 0 volts then slowly adjust the variable attenuator balance control to force pin 6 of V244 and V254 to more of less equal which should bring trace on screen. If the voltages are OK and still no trace then make sure sweep is free running.

[Ice-Tea]

the postman just rang. twice ...

....

cost was 155 Pesos incl postage

Thats a steal!

[med6753]

The RM17 vertical pre-amp and final amp.

[Specmaster]

Driver frozen up is a very common failure mode; I've replaced more than I can count. 

That's when the recone kit comes out. Such things do exist. I've done more JBL 2220 and 2225 15" drivers than I can count. Although, for a simple 6" car woofer, not likely to find one. Aftermarket foam surrounds, though.  That is a thing.

Get a pair of cheap aftermarket 4Ω speakers the right size and replace both so the sound is the same. If that speaker measures 2Ω DCR, actual impedance will be a bit higher; more like 2.5-3Ω. Inversely, a 4Ω impedance speaker will usually measure 3-3.6Ω DCR.

2Ω might be a battered 4Ω too.  I've done a few in-door replacements, and there's one coming up soon here. What I usually do, is to go to used parts dealers and buy from scrapped cars. For a lot of non-wear items (and a good deal wear items too) this is a very convenient and cheap way to prolong the life of your car.  In Sweden, there's a common online database service for about 150 dealers where you can search on mfr part number and find who's got it. Very, very effective and convenient.

Under any circumstances, in most cases using a lower impedance speaker will do nothing except decrease max volume a bit and make the amp run a bit cooler.

Now, lowered impedance, if we for a while play "DC == AC" simplification game, means more current. More current usually means hotter transistors. The limiting factor for output power is rail voltage, which will set an output level at which clipping happens. In an ideal amplifier, half the load impedance means double current at a fixed max voltage, doubling the output power, and making the amp run hotter. Less than ideal amplifiers usually mean that the power supply can't supply enough current, or the transistors won't deal with the power levels, placing a limit on how low load impedance safely can be.

I'm quite bad at electronics, and I only have professional user experience of power amplifiers, but this is what I learnt during perhaps 20 years doing such things on and off.

So, how come you predict the amp will run cooler? And then we've not discussed any passive crossover point moving because the impedance is a part of the filter..

Hmm, I don't think that reconing would be an option in this case, even if one was available, as the speaker itself is so different. The entire frame is all plastic and the speaker cone is some 50mm in front of its mounting flange so normally constructed speakers will not of use as there is zero space in the door cavity itself, it all resides within the moulded door card, the mid-range speaker is mounted directly to the door card and the tweeter is housed within the door cavity.

This is repeated for all 4 doors. The stereo system is the top of the range and was an optional extra when the car was purchased, the standard car stereo has 4 speakers which I can source 2nd hand with ease on eBay, 2 for a similar cost to 1 of the 2 speakers from Germany. Question is however, is how will these affect the overall sound and volumes in the car, because as you mentioned the crossovers have been calibrated to work correctly with 2 ? They will take less current to drive them, is this going to cause problems within the amp?

[med6753]

Vince, I looked over the schematic for the RM17 and it appears from your description that the vertical amp is out of balance. Here's what I recommend to check it:

Set Trigger to Auto and Preset. That should cause the sweep to free run.

No signal on vertical input. Short the input to the chassis.
DC coupling, 0.2v, variable to calibrated.
Set vertical position to mid-range.

Check pin 6 of both V244 and V254. DCV should be equal or nearly equal. A large difference between them will force trace off screen.
Check pin 2 and 7 of V233A/B. Again, DCV should be equal or nearly equal.
Check pin 1 of V183 and V203 for 0V. If pin 1 of V203 has any voltage then coupling capacitor C171 is leaky and the source of your imbalance.
If all those checks are OK then slowly adjust the variable attenuator balance control to bring the trace on screen. Check that pin 6 of V244 and V254 become more or less equal. If they are and you still have no trace then make sure the sweep is free running.   

Edit......Last statement is incorrect. Should read: If there is a large difference in voltage yet V183 and V203 are 0 volts then slowly adjust the variable attenuator balance control to force pin 6 of V244 and V254 to more of less equal which should bring trace on screen. If the voltages are OK and still no trace then make sure sweep is free running.

I should have been fully awake before I typed this mess. See schematic. If the variable attenuator balance control is way off it will also introduce a voltage into pin 1 of V203 which will throw the entire vertical amp out of balance.

[med6753]

My faith in USPS has been restored. The wayward package went from Phillipsburg NJ to Albany NY distribution center, then to Newburgh NY distribution center, and to my PO this morning. So as long as my local PO doesn't fumble it I should have the package today. 

[AVGresponding]

Driver frozen up is a very common failure mode; I've replaced more than I can count. 

That's when the recone kit comes out. Such things do exist. I've done more JBL 2220 and 2225 15" drivers than I can count. Although, for a simple 6" car woofer, not likely to find one. Aftermarket foam surrounds, though.  That is a thing.

Get a pair of cheap aftermarket 4Ω speakers the right size and replace both so the sound is the same. If that speaker measures 2Ω DCR, actual impedance will be a bit higher; more like 2.5-3Ω. Inversely, a 4Ω impedance speaker will usually measure 3-3.6Ω DCR.

2Ω might be a battered 4Ω too.  I've done a few in-door replacements, and there's one coming up soon here. What I usually do, is to go to used parts dealers and buy from scrapped cars. For a lot of non-wear items (and a good deal wear items too) this is a very convenient and cheap way to prolong the life of your car.  In Sweden, there's a common online database service for about 150 dealers where you can search on mfr part number and find who's got it. Very, very effective and convenient.

Under any circumstances, in most cases using a lower impedance speaker will do nothing except decrease max volume a bit and make the amp run a bit cooler.

Now, lowered impedance, if we for a while play "DC == AC" simplification game, means more current. More current usually means hotter transistors. The limiting factor for output power is rail voltage, which will set an output level at which clipping happens. In an ideal amplifier, half the load impedance means double current at a fixed max voltage, doubling the output power, and making the amp run hotter. Less than ideal amplifiers usually mean that the power supply can't supply enough current, or the transistors won't deal with the power levels, placing a limit on how low load impedance safely can be.

I'm quite bad at electronics, and I only have professional user experience of power amplifiers, but this is what I learnt during perhaps 20 years doing such things on and off.

So, how come you predict the amp will run cooler? And then we've not discussed any passive crossover point moving because the impedance is a part of the filter..

I think the tinkerdwagon posted this before his required coffee intake. The point of lower impedance speakers for automotive applications is to get more power out of them within the limits of the low voltage power supply available (excepting certain aftermaket stuff with inverters to boost the supply rails), this also being why BTL (bridge tied loads) became widely used (this is where instead of a phase and ground, you feed phase and counter-phase to the speaker).
2Ω and even 1Ω speakers are quite common in car audio nowadays.

[BU508A]

My faith in USPS has been restored. The wayward package went from Phillipsburg NJ to Albany NY distribution center, then to Newburgh NY distribution center, and to my PO this morning. So as long as my local PO doesn't fumble it I should have the package today. 

I hope, it will not turn out like this: