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SSE first build, caps and other questions.

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#202
YashN said:
Could it be I messed up the grounding? My OPT Primary, Seconday and Grounding schemes are as in #1 (but have no choke).

Looking at the grounding in this diagram:

Triode%20no%20CFB_zpsatpwflgf.png


The grounding is: Both speaker -ves to star ground and one input -ve to star.

In the following diagram (no choke, CFB, UL), the grounding is much simpler:

UL%20Nochoke%20CFB_zps6lpsuada.png
Click to expand...
The grounding at the inputs is the same on both of those.
You haven't mixed up the -ve and the + ve on the right input have you ?
the 2 -ve are in the centres.
Or if a catastrophic short caused this as you said, there may well be some damage shorting out your input connectors or input wires.
 
#204
w5jag said:
I hope you've found it.
Click to expand...

I found something very fishy indeed!

Since it can't be right that my +ve on the right input shows a short to -ve, I decided to look further into that: so either circuit or inputs.

I traced continuity of the circuit around inputs and the driver, it's all good.

Hence I had to diagnose the input module and for that, to ensure I can diagnose it alone, I disconnected the +ve from the main PCB.

Now, even then, a continuity test showed a short on +ve to -ve!

Here is what happened: this input module is something from my salvage box. In the left side, the PCB has been thoroughly cut so that 3 little independent 'islands' of PCB remain. No short there.

However, on the right input, there is a single piece of PCB remaining underneath the RCA input.

This should be fine, except when I checked more closely, the actual GND plane was designed to be quite encompassing and wraps around the +ve with just a really small gap, a hairline really.

So guess what happened with a solder blob there... SHORT!

I though this was an easy fix: Dremel along the way to isolate the islands, but tests still showed a short, so I had to pump solder, Dremel, Scalpel as well as actually cut PCB bits with pincers.

OK, so now, after testing, this is fixed (finally!).

Re-test of the amp: right channel still fails. Left channel still sounds glorious as to attack transients and dynamics despite the very bad test speakers.

So, not everything fixed, but this one was a *must* to be fixed.

Looking forward to fixing the rest.

TGIF and enjoy drinks and the week-end!
 
#205
We like to hear success stories. Congratulations. I had a short to ground on my SSE build using point to point instead of the boards on one channel as well. The solder tags I was using has one tab that goes to ground that I usually bend over so I will not use that one but I did forget and used it for a connection point. Took a few hours of testing before I found the problem.
 
#206
wdecho said:
We like to hear success stories. Congratulations. I had a short to ground on my SSE build using point to point instead of the boards on one channel as well. The solder tags I was using has one tab that goes to ground that I usually bend over so I will not use that one but I did forget and used it for a connection point. Took a few hours of testing before I found the problem.
Click to expand...

Thanks for the encouraging words, even though I think it's not much of a success for me yet:

Firstly, my problem still remains - right channel is down.

Secondly, had I tested this input first properly, I wouldn't have spent time with the circuit, which is far more difficult.

This said, I would have had to diagnose the circuit anyway, so I'm back to starting point but now with more knowledge.

But at least it's a good starting point for the rest of the troubleshooting.

I am thinking of doing the measurements again.
 
#207
I'm sorry I misread the post and thought you had solved the right channel problem. Persevere and you will find it. Get the voltage readings on those output tubes for members to look at. It would not surprise me if you do not have the same problem as I had a grounded signal input going into the grid of the output tube preventing the signal from getting in. check that circuit board again with a magnifying glass for a solder bridge. Anywhere there are leads close together check especially close.
 
#210
Coupling Cap connection test

gcom said:
It may be worth pulling a leg on each coupling cap again at this stage and crossing the channels, to be sure that your right output stage is still OK.
Click to expand...

Come stai, gcom? 😀

I re-did the test for the coupling caps connection as mentioned by George (didn't lift their legs here):

Looking at the board from the top side with it oriented so that the "Tubelab Simple SE" printing is right side up, run a temporary jumper wire (solder a wire, or use a clip lead) from the left side of one coupling cap to the other (C11 and C21). It can be on either side of the board, but it must be on output side of the caps. This allows either driver circuit to feed both output circuits.

Connect the board up in the usual manner and test it. Is there sound from both speakers? If yes, the problem is in the input section.
Click to expand...
Both speakers work, just as before, so my output section is OK and we narrowed down the issue to the input section as before.

Now, I also want to try this second test but it isn't clear to me whether I should try this one with the jumper above still in place or removed:

If the input section is at fault, the usual place is the wiring from the input connections to the volume pot and input connectors. Temporarily connect the two outer terminals of the input connector on the PC board together. If both channels work, or neither work the input wiring is at fault
Click to expand...
 
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#213
Corrected Readings for KT-88

[NB: of course, I messed these up, so here are the corrected ones - disregard post 211 above], here are the measurements for the KT-88 and resistors below:

1. Left P8: 41.3 VDC
2. R27: 41.7 VDC
3. Right P8: 41.2 VDC
4. R17: 41.2 VDC

Furthermore, I measured P3 for each KT-88:

5. Left P3: 417 VDC
6. Right P3: 418 VDC
 
#215
cjkpkg said:
Those look spot on
Click to expand...

Thanks man.

Armed with a little bit more knowledge about terminology and practical experience, I am going over your suggestions again, and I am going to try these as first steps:

(a) Swap coupling capacitors
(b) Check Grid Stoppers: Right R12

Then, I would like to follow your suggestion of tracing the current path/measuring across different points, but will probably have a couple of questions for you along the way to make sure I am doing these properly.

Thanks again.
 
#217
Thanks.

I swapped the coupling capacitors, Solen caps rated at 600V, and the left channel still works and the right channel is still down.

This means that the old coupling Cap on the right channel is still OK, and that means both of them are OK.

I removed R12 and it is measuring OK at around 101 Ohms.
 
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#219
This is correct, and all in VDC, right?:

Voltage from cathode to ground 12at7 Right - taken at the socket then to a ground point -> P3
Voltage across the cathode resistor 12at7 Right -> both before and after R10

Voltage from cathode to ground 12at7 Left - taken at the socket then to a ground point -> P8
Voltage across the cathode resistor 12at7 Left-> both before and after R20
 
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