Test Equipment Anonymous (TEA) group therapy thread

[Brumby]

All switches have been de-oxed and confirmed fully operational, so no crusty contacts, there, all pots have been cleaned as well, so back to the bench tomorrow, hopefully unless until SWMBO finds me something to do.

Let's be real.    FTFY.   

[med6753]

Local CL has this Heath SB-301 for $90. Made me pause for a moment then dismissed it. Why? Well, it was a kit. Build quality is definitely a crap shoot. And who knows if it ever worked properly when it was complete. That's a definite consideration. I'll pass but I did give it some thought.

I've seen worse....much worse.

Seller has reduced this from $90 to $70. It's making me twitch but still no go. 

Let the seller rot for a couple weeks and offer him 55 bucks....

In order for that twitch to become overwhelming it would have to go to $50 or less. I'm sure now that he reduced the price one of the local unwashed hobo hams will snap it up.

[med6753]

All switches have been de-oxed and confirmed fully operational, so no crusty contacts, there, all pots have been cleaned as well, so back to the bench tomorrow, hopefully unless until SWMBO finds me something to do.

Let's be real.    FTFY.   

I rejoice everyday that I have no SWMBO. 

[Vince]

If I were you I would stop bragging because... I am sure soon enough Lady cop will retire, and she will manage to come up with some sort of rationale to convince you that she needs to move in.
Obviously it will be done with subtlety and she will manage to manipulate you so well that you might even think it's YOUR decision, so that you don't even fight it. It's an art.

THEN you will have a SWMBO....

I say, enjoy your freedom while you still can, it won't last long 

[vk6zgo]

I am just done oiling my brand new oak parquet in the bedroom.

<snip>

So no... no no no ... NO !

<snip>

Now, do I look like the kind of man who would sit back and smugly say "Told you so"?

SNIP

Yes, yes I do look like that kind of man.

So all in all... it was quite an experience. Next time I oil that parquet (recommendation are once or twice a year I gather), I will just do it manually like I just did... sacrifice a towel, and kneel down, and rub, rub...     Thank goodness the room is only 10m2 ! 

Once the whole thing is sealed "topping off" the finish with a little oil is easy. It only needs a tiny amount, no more than just enough to wet the surface evenly.

I wish you'd shouted "help!" earlier. For the future reference of others, the standard approach to oiling hardwood is:

(1) Apply an initial coat diluted with white spirit (aka mineral turpentine, mineral spirits, whatever it's called where you are). Dilution ratio is not critical, just enough to make it wipeable rather than gloopy and not so dilute that you're hardly applying any oil. 10%-50% white spirit as a seat-of-the-pants guess.
(2) Leave 15 minutes to soak in.
(3) Wipe off with a clean dry rag.
(4) Leave 24 hours to dry.
(5) Wipe over a thin coat of neat oil. Enough to guarantee that you wet out the surface.
(6) Leave 15 minutes to soak in.
(7) Wipe off with a clean dry rag.
( Leave 24 hours to dry. [That's a 8 followed by a bracket, but SMF is stupid]
(9) Have you got the level of finish you want? Of so, go to 10, if not go to 5.
(10) Drink beer.

Interestingly, White Spirit & Mineral turps are different things in Oz, with the former being a fairly bland fluid, with little odor, whereas the latter has a strong odor. Another difference is that White Spirit dries cleanly, & Mineral Turps leaves an oily residue.
The local Coles supermarket is even more confused----- they supplied me with two bottles of MT as substitutes for my online order for Methylated Spirit.

Your descrition of mineral turpintine sounds like genuine turpintine. Various sources say mineral turpintine is the term for white sprit in NZ/AUS.  Maybe your supplier is repacaging the wrong stuff.  In the UK mineral turps is sometimes called turpintine subsitute but white spirit is more common these days.  Another, more technical description is stoddart solvent. This contans a specified percentage of > C10 hydrocarbons, They are basically all highly refined kerosine.

The "sources" are wrong, at least as far as Oz is concerned---I can't speak for NZ.
My Mother was, & my sisters are, artists. They use real turps for oil paintings, as Mineral Turps doesnt work well.
The real thing is a lot thicker, darker, & stronger smelling.
MT is used by house painters to thin oil based paint----they wouldn't touch "White Spirit".

[med6753]

If I were you I would stop bragging because... I am sure soon enough Lady cop will retire, and she will manage to come up with some sort of rationale to convince you that she needs to move in.
Obviously it will be done with subtlety and she will manage to manipulate you so well that you might even think it's YOUR decision, so that you don't even fight it. It's an art.

THEN you will have a SWMBO....

I say, enjoy your freedom while you still can, it won't last long 

Nope. Won't happen.

[Andrew_Debbie]

Local CL has this Heath SB-301 for $90. Made me pause for a moment then dismissed it. Why? Well, it was a kit. Build quality is definitely a crap shoot. And who knows if it ever worked properly when it was complete. That's a definite consideration. I'll pass but I did give it some thought.



I've seen worse....much worse.

Seller has reduced this from $90 to $70. It's making me twitch but still no go. 

I'd be slightly tempted if I was local.  All three filters are present as well as all the crystals.   It is certainly a candidate for a teardown and rebuild.  As I vaguely  recall the SB-301 is ham bands only.     Edit, Downloaded the manual, - yes Ham Bands  from 80m to 10m.  There is someoverlap with broadcast bands.       1N191 Ge diode in the AM detector.  Have not checked availability. 

Google found me this  re-cap kit.  $43.75   They also sell the can capacitor separately.

https://hayseedhamfest.com/products/sb-301-re-cap-kit

[med6753]

I'd be slightly tempted if I was local.  All three filters are present as well as all the crystals.   It is certainly a candidate for a teardown and rebuild.  As I vaguely  recall the SB-301 is ham bands only.     Edit, Downloaded the manual, - yes Ham Bands  from 80m to 10m.  There is someoverlap with broadcast bands.       1N191 Ge diode in the AM detector.  Have not checked availability. 

Google found me this  re-cap kit.  $43.75   They also sell the can capacitor separately.

https://hayseedhamfest.com/products/sb-301-re-cap-kit

You're right. I forgot it was ham bands only. That settles it. Let the hobos have it. 

[Specmaster]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

[Saskia]

finickled a Marantz showroom rack into Hubby's lair (eff me, that thing has 150 kg ... with a steel frame).
Lugged 2 Arcade1ups upstairs, also lugged the Festool MFT/3 that got here (how did that happen ...) upstairs. Made plan for electrical wiring of upstairs as well as putting in flooring. Still waiting for the table saw stand and the miter saw.

Wrote Vodafone DSL cancellation letter - way overdue, but better late than never.
2 more admin things due today, also still some unpacking and sorting to do.

[med6753]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Your sweep signal should look similar to this coming into the horizontal amplifier. The ramp speed will vary with the Time switch. No ramp, no sweep.



Edit....an example of a good sweep signal.

[Vince]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Looks like the Horizotnal amplifier has problems too...
I had a similar/identical problem as you have, on my glowing Tek 502A (the first one not the one I bought recently), and there was no sweep issue in the end... it was all due to the H amp section. One of the tubes was dead in the amplifier, which cut the signal. The dead tube of course created a huge imbalance which explained why the dot could be move way off screen in one direction, but that travel was way insufficient on the right side...

Regardless you need to probe the signal path where the amp and sawtooth generator meet, so you know what part of the chain is at fault..

Of course given the huge accessibility issues on this scope, I would maybe change the technique a bit, and look for the low hanging fruits first : probe as much stuff as you can, whole still relevant of course, with the scope as is, still assembled. Looking at your pics there is a fair amount of components accessible enough for a probe to reach them (vertical boards or main / horizontal board). Also all the switches on the front panel look like their terminals go through their white cases and are exposed, so lots of probe points right there for your to look at.

Once that's done I would take the time /effort to pull the guts of the scope out of the bottom case, so that you can access the bottom of the main board, hence all the interconnect points where the vertical boards meet the main board. Surely there must be interesting / worthwhile things to probe there.

Good luck...

[Specmaster]

So far I have found nothing that produces a usable trace, I have had a quick prod with a probe and only found so far the calibration test signal which is of course dead nuts at 1V pk-pk.

Access when fully assembled is extremely limited at best and worst it is totally impossible with components mounted on end in order to cram it all in to keep the footprint small. This was designed well before the dawn of SMD technology but needed to keep real estate down in order to reduce costs 

Off to go shopping now, will continue probing and tracing on my return.

EDIT:
Just did a quick probe around IC8 which produces a lovely sawtooth of around 1Vpk-pk at 18-19KHz only to realise of course that is for the SMPS which is working, will check the other generator IC1 on my return, but first I need to locate my caftan tape as the pins are so close to other parts that a probe slip could spell mayor probelms.                                                                                                                                                                                                                                                             

[factory]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Could the -493V instead of -540V be loading from the meter you used to test it? It's not shown on the diagram but the description refers to it being referenced to R605/606, i.e. the top of the focus pot VR601 & divider resistors R607/608. These will put between 10MΩ & 14.7MΩ in parallel with your meter, the -540V supply has a series resistor before the rectifier (can't read the number).

You should be able to test the external X input separately as I was referring to yesterday, this mode grounds the timebase sweep via the "trig sweep/ext X" switch, in ext x mode.
In sweep mode you should be able to see the signal at the switch on pins 1 & 4.
Hopefully this will allow you to work on the faults separately if there are two.

The manual is available from BAMA, someone has translated it to French too. https://bama.edebris.com/manuals/sinclair/sc110/

[mnementh]

For those playing along at home:



mnem

This PSA brought to you by SPHAPPP (Pronounced ess-Fapp )

(the Society for the Prevention of HAM Hobos Apoplectically Proselytizing in Public Places)

[mnementh]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Could the -493V instead of -540V be loading from the meter you used to test it? It's not shown on the diagram but the description refers to it being referenced to R605/606, i.e. the top of the focus pot VR601 & divider resistors R607/608. These will put between 10MΩ & 14.7MΩ in parallel with your meter, the -540V supply has a series resistor before the rectifier (can't read the number).

You should be able to test the external X input separately as I was referring to yesterday, this mode grounds the timebase sweep via the "trig sweep/ext X" switch, in ext x mode.
In sweep mode you should be able to see the signal at the switch. Hopefully this will allow you to work on the faults separately if there are two.

The manual is available from BAMA, someone has translated it to French too. https://bama.edebris.com/manuals/sinclair/sc110/

Nooooo!!!

You want the version I just submitted to BAMA; Ed eMailed me the other day that it's posted here (Right-Click, Save As, etc):

http://bama.edebris.com/download/thandar/sc110a/Thandar_SC110A_Oscilloscope_Service.pdf

This version actually has legible schematics, unlike the version which is visible from the page you posted.

I figured I'd give the poor guy a couple-three weekends to get around to updating the site so the Sinclair landing page points to the SC110A .pdf as well.

mnem
 

[factory]

Will have a look later, but I'm sure it's the non A version he's working on.

David

[mnementh]

Yeah, okay... I guess that's a tough call... illegible correct schematics vs legible ones for a later revision...   



But in this case... the first one is pretty close to useless. 

So I guess you need both... and hope you can extrapolate successfully whatever part of the circuit you're working on. 

mnem
The fixer's lament...

[AVGresponding]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

You might want to get some contact cleaner in the TIME/DIV rotary switch contacts; mine will drop sweep due to that if I don't use it for a while. If it turns out not to be that, I can do some comparison measurements for you.

[Specmaster]

For those playing along at home:



mnem

This PSA brought to you by SPHAPPP (Pronounced ess-Fapp )

(the Society for the Prevention of HAM Hobos Apoplectically Proselytizing in Public Places)

Don't like condoms  they spoil the fun 

Seriously in this situation, the condom would literally mean I would be unable to contact the legs of the IC as the width of the probe + condom would prevent it

[mnementh]

Maybe a wee bit of Kapton tape on probe pin and around ground ring?

mnem
 

[Specmaster]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Could the -493V instead of -540V be loading from the meter you used to test it? It's not shown on the diagram but the description refers to it being referenced to R605/606, i.e. the top of the focus pot VR601 & divider resistors R607/608. These will put between 10MΩ & 14.7MΩ in parallel with your meter, the -540V supply has a series resistor before the rectifier (can't read the number).

You should be able to test the external X input separately as I was referring to yesterday, this mode grounds the timebase sweep via the "trig sweep/ext X" switch, in ext x mode.
In sweep mode you should be able to see the signal at the switch. Hopefully this will allow you to work on the faults separately if there are two.

The manual is available from BAMA, someone has translated it to French too. https://bama.edebris.com/manuals/sinclair/sc110/

Nooooo!!!

You want the version I just submitted to BAMA; Ed eMailed me the other day that it's posted here (Right-Click, Save As, etc):

http://bama.edebris.com/download/thandar/sc110a/Thandar_SC110A_Oscilloscope_Service.pdf

This version actually has legible schematics, unlike the version which is visible from the page you posted.

I figured I'd give the poor guy a couple-three weekends to get around to updating the site so the Sinclair landing page points to the SC110A .pdf as well.

mnem
 

But that is the same manual that I'm using, the one you gave me the link to, and as factory (David) correctly said, it is the SC110 I have (not A or B) but sadly all the manuals I can locate have all been for the A model

[Specmaster]

Maybe a wee bit of Kapton tape on probe pin and around ground ring?

mnem
 

Correct, that was what I was referring to when I mentioned caftan tape, I got the name wrong, my bad.

[tautech]

@Vince and @Med6753, thanks for your inputs on the SC110, Vince you are correct, the -493V is only in the CRT section, it does not propagate anywhere else  and as I do have a dot on the screen which is both bright and sharp, also can be moved using the X and Y controls, then the CRT is OK.

With the input selector set on the lowest positions, the dot becomes 2 dots, which shows that the vertical is OK, and the 2 dots represent the top and bottom of the trace. There is zero sweep on the screen. Using the X control, I move the dot(s) off the screen to the left and only slightly past the centre of the screen with the control fully clockwise. As I move the X control anticlockwise, the dots move further apart, and you can see a faint trace between the dots. If I select DC on the input then only the top dot moves upwards as I rotate X control anticlockwise, the bottom dot remain at the same level which is correct. Pressing both AC and DC input selectors to get a grounded signal the dots revert a single, again indicating no sweep.

Looks like the Horizotnal amplifier has problems too...

Don't discount the sweep being very nonlinear.
Not only must it be there it must also be a clean ramp/sawtooth and it pays to check it over a range of s/div settings.
Been there and earned the T shirt. 

Maybe a wee bit of Kapton tape on probe pin and around ground ring?

mnem
 

This or use some grabbers with short flying leads connected to your probe tip.

[Specmaster]

Wow, I tried to look for a Sinclair SC110 and found the service manual for that model, not the A variant. Now to see what if any are the differences between the two?

Strange though as mine has Thandar on the enclosure but Sinclair on the main PCB but the control panel is nameless??