Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Final picture as most of the ones I've posted are it lying arse up!



Edit: so scope situation:

1. HP 1740A - working
2. Philips PM3217 - working
3. Hameg HM203 - working
4. Rigol DS1054Z - working
5. tektronix 475 - working
6. incoming Telequipment D75 - not working.

That's a good turnout. So, which one do you think is going to break first? 

[med6753]

Thought it was a pass transistor but it was the drive current from the LM723. I stuffed a DMM in series with base and it was only driving 4mA through whereas for the beta it should have been about 30mA. That was causing rails to collapse.

Anyway made a heatsink quick. Took longer to get the bloody screw in than make the heatsink. Disclaimer: I have zero metalworking tools here so this was literally aviation shears, file and hand drill

Hey, that will work. Not a bad bodge at all. 

This 465B has been cluttering up bench 1 for 2 days now untouched. Gotta get my arse in gear here. Today's mission is to get the old capacitors out without destroying the board....or myself. 

[med6753]

Final picture as most of the ones I've posted are it lying arse up!



Edit: so scope situation:

1. HP 1740A - working
2. Philips PM3217 - working
3. Hameg HM203 - working
4. Rigol DS1054Z - working
5. tektronix 475 - working
6. incoming Telequipment D75 - not working.

That's a good turnout. So, which one do you think is going to break first? 

Shut your mouth. 

[bd139]

Hahahaha 

[dcbrown73]

Just picked up a Sencore LC75 with SCR250 SCR and triac tester.   



Guess this means my Peak ESR70 will be relegated to mobile use. 

[bd139]

FFS I was going to buy a Farnell L30BT power supply as a beater but I forgot to bid on the damn thing 

[Specmaster]

@bd139, great job with the 1740A looks like great win there 

I've been working on the SU-V2X amp again, it had noisy left channel with a low burbling noise and low gain, thinking that it was probably, a cap, I've pulling them out and checking and found nothing at all. There was a spot of some sort of spillage on the PCB so while clean, the transistor got slightly touched and then I found what I believe to be the problem. The spillage had corroded the base leg of a transistor right beneath its body, new one on order, so hopefully if the Ebay offer is on next week I'll be flipping it again.

[bd139]

Glad that Lucas aren't in the semiconductor business still. They'd just sell that as a TO92 diode 

[worsthorse]

@bd139, great job with the 1740A looks like great win there 

I've been working on the SU-V2X amp again, it had noisy left channel with a low burbling noise and low gain, thinking that it was probably, a cap, I've pulling them out and checking and found nothing at all. There was a spot of some sort of spillage on the PCB so while clean, the transistor got slightly touched and then I found what I believe to be the problem. The spillage had corroded the base leg of a transistor right beneath its body, new one on order, so hopefully if the Ebay offer is on next week I'll be flipping it again.

That PCB looks like it has had a hard life.   

[med6753]

I can't tell you how much fun this is. Like going to the dentist. Got 2 of the capacitors pulled so far. What a royal pain in the gonads. And one land pattern pulled up as a bonus.  Luckily super glue fixed that. 3 more to go. I knew these were going to be difficult but geeeez. 

[worsthorse]

The schematics for the B+K 2831D appear to have been drawn by someone who never had to read a schematic. Ever. And added it to the service manual when no one was looking. Missing connections. Random symbols. Unlabeled connections.  A bypass capacitor that appears to short a resistor that determines the input impedance when measuring AC voltage. I imagine that some poor customer service tech had a dog-eared, much marked up version that allowed one to actually work on it.

But it is sort of fun figuring stuff like this out, at least when I am not getting paid to do so. Which is good because I will spend more time fixing the schematic than I will fixing the DMM.   

[mnementh]

In Other News...

OH MY FUCKING GAWWD!!! I CAN SEE THE LIVING ROOM FLOOR!!!

mnem
*small moving-time victory number 57*

[mnementh]

Thought it was a pass transistor but it was the drive current from the LM723. I stuffed a DMM in series with base and it was only driving 4mA through whereas for the beta it should have been about 30mA. That was causing rails to collapse.

   Anyway made a heatsink quick. Took longer to get the bloody screw in than make the heatsink. Disclaimer: I have zero metalworking tools here so this was literally aviation shears, file and hand drill

Looks like OEM from the guys who made my KSGER T12 soldering station. 

Any reason you're not replacing with a larger rectum-frier that isn't operating so close to max tolerance?

mnem
 

[bd139]

Thought it was a pass transistor but it was the drive current from the LM723. I stuffed a DMM in series with base and it was only driving 4mA through whereas for the beta it should have been about 30mA. That was causing rails to collapse.

   Anyway made a heatsink quick. Took longer to get the bloody screw in than make the heatsink. Disclaimer: I have zero metalworking tools here so this was literally aviation shears, file and hand drill

Looks like OEM from the guys who made my KSGER T12 soldering station. 

Any reason you're not replacing with a larger rectum-frier that isn't operating so close to max tolerance?

mnem
 

Unfortunately it’s a weird ass 0.156 pitch rectifier which is obsolete by about 20 years this the options were limited. That tiny little POS was 6A rated if I remember correctly. But you have to nail it to something. It’s pulling ~560mA average through it.

I actually had to buy a whole tube of 50 of the damn things just to get one. Figured I’d use the rest in the future one day!

[Specmaster]

@bd139, great job with the 1740A looks like great win there 

I've been working on the SU-V2X amp again, it had noisy left channel with a low burbling noise and low gain, thinking that it was probably, a cap, I've pulling them out and checking and found nothing at all. There was a spot of some sort of spillage on the PCB so while clean, the transistor got slightly touched and then I found what I believe to be the problem. The spillage had corroded the base leg of a transistor right beneath its body, new one on order, so hopefully if the Ebay offer is on next week I'll be flipping it again.

That PCB looks like it has had a hard life.   

It has in that area, coke was spilled over it through the top vents of the amp and I'd just been trying to clean the sticky gunge off, still see some in the holes.

[med6753]

They're out, finally. And with only one fubar'ed land pattern which has been repaired. 100% IPA to remove all the flux. Tomorrow new install and power up.   

[bd139]

That looks pretty tidy 

Going to have to do the same this week with the D75 and the boards in it are single sided non plated through ones 

[xrunner]

Oh my - those are some tall ones. 

[med6753]

Oh my - those are some tall ones. 

The replacements are so small in comparison that you wonder if they will work. 

[xrunner]

The replacements are so small in comparison that you wonder if they will work. 

Oh yea much better capacitor technology/manufacturing now - can you place some side-by-side for comparison?

[med6753]

The replacements are so small in comparison that you wonder if they will work. 

Oh yea much better capacitor technology/manufacturing now - can you place some side-by-side for comparison?

Sure, give me a few minutes and I'll put the replacements with the old ones.

[med6753]

The replacements are so small in comparison that you wonder if they will work. 

Oh yea much better capacitor technology/manufacturing now - can you place some side-by-side for comparison?

Sure, give me a few minutes and I'll put the replacements with the old ones.

[xrunner]

Sure, give me a few minutes and I'll put the replacements with the old ones.

Yep - that's about the size of it (no pun intended). Way smaller and more reliable too. 

[dcbrown73]

Those are too small.  Not gonna work.   

[bd139]

 

Just buy some from Aliexpress!