Dumble - help needed urgently!

[drew]

This D'Lite layout has expected/typical voltages noted at various places; may be of some help as a reference to see if you're in the ballpark: http://www.brownnote.net/forum/download ... &mode=view

The sporadic noises might be a dry solder joint. If you look at all the connections really closely -- with a magnifying glass, if you have one -- and you see one that looks grainy or dull instead of shiny, try re-flowing it.

Congrats on getting this far with such minimal problems (knock on wood). How does the thing sound?

[Mousey Dung]

This D'Lite layout has expected/typical voltages noted at various places; may be of some help as a reference to see if you're in the ballpark: http://www.brownnote.net/forum/download ... &mode=view

Super! I'll check that out.

The sporadic noises might be a dry solder joint. If you look at all the connections really closely -- with a magnifying glass, if you have one -- and you see one that looks grainy or dull instead of shiny, try re-flowing it.

Seems like something minor along those lines, probably some solder splatter or loose strands somewhere...

Congrats on getting this far with such minimal problems (knock on wood).

Thanks! I'm so relieved it's nearly over now...

How does the thing sound?

I don't really know yet, as my wife is asleep upstairs. I'll give it a proper test tomorrow with a better speaker.

[Mousey Dung]

So all switching functions are 100% correct?

Yes, they seem to be working fine, although I won't know for sure until tomorrow, when I turn it up properly. Right now my wife is asleep upstairs :-p

What are you doing for a footswitch?

I have a footswitch unit with three switches and LED lights. It seems to be plug-and-play ready.

If all functions are correct, I would document voltages and then start to chase crackling gremblins with a shakedown test of the wiring.

Where can I find an outline of specific procedures for the measuring the tube pins? (for ex. measuring AC voltage between power-tube pins 2 and 7)

[Mousey Dung]

I would systematically go through the controls and switches to see if they are all functional. Have you got reverb?

Connected in reverb, but can't get any

Where did the tube voltages settle out? It would be a good idea to get a set of measurements from the power supplies and the tube pins.

Are you referring to the bias test-point mV measurement or the different pins on each tube? For the latter, I think I'm not always supposed to measure each pin against the ground... surfing Internet for info, can't find it yet...

[drew]

Are you referring to the bias test-point mV measurement or the different pins on each tube? For the latter, I think I'm not always supposed to measure each pin against the ground... surfing Internet for info, can't find it yet...

You don't need to worry about the bias or the heaters - you've checked those and they're fine. Re-measure the points on the cap board that Martin had you do before the tubes were installed, and measure those points along the bottom row of the preamp board that have the voltage readings in that diagram I linked to above (plus the analogous points on the additional preamp tube that your amp has). Meter set to DC volts, black lead grounded, use only one hand to take measurements; keep other one in your back pocket.

[martin manning]

On the voltages, you can just get the seven points on the power supply board for the supply voltages, then power tube pins 3, 4, and 5, and preamp tube pins 1, 2, 3, and 6, 7, 8. All DC, all to ground.

The voltages on the reverb tube pins might give a clue as to why it's not working. To diagnose further, you should be able to hear the signal coming out of the driver side RCA jack by connecting it to a speaker, and if you plug a cable into the recover side jack and tap the center pin on the open end with your finger, you should hear a buzz, like doing the same with a guitar cable plugged into the amp's input.

[Mousey Dung]

DC voltages with standby switch off:
- Relay supply: 11
- B+ plate supply: 488
- Bias supply: -63
- Power amp5-V8 plates: 487

DC voltages with standby switch on:
- Relay: 12
- B+ plate supply: 459
- Bias supply: -63

- Power amp5-V8 plates: 459
- Power amp V5-V8 screens: starts at 476, settles at 458
- Clean V1 plates: 327
- OD V2 plates: 334
- Phase inverter V4 plates: 445
- Reverb rectifier V3b plate: 442
- Reverb driver Trans/V3a plate: 396

- V8 pin 3: 459
- V8 pin 4: 458
- V8 pin 5: -42

- V7 pin 3: 459
- V7 pin 4: 458
- V7 pin 5: -42

- V6 pin 3: 458
- V6 pin 4: 457
- V6 pin 5: -43

- V5 pin 3: 458
- V5 pin 4: 457
- V5 pin 5: -43

- V4 pin 1: 276
- V4 pin 2: 29
- V4 pin 3: 44
- V4 pin 6: 266
- V4 pin 7: 28
- V4 pin 8: 44

- V3 pin 1: 269
- V3 pin 2: 0
- V3 pin 3: 2
- V3 pin 6: 392
- V3 pin 7: 0
- V3 pin 8: 3

- V2 pin 1: 209
- V2 pin 2: 0
- V2 pin 3: 2
- V2 pin 6: 206
- V2 pin 7: 0
- V2 pin 8: 2

- V1 pin 1: 203
- V1 pin 2: 0
- V1 pin 3: 2
- V1 pin 6: 199
- V1 pin 7: 0
- V1 pin 8: 2

[martin manning]

Woo hoo! Looking good there, and your well-organized table makes the assessment easy (others take note!).

Seems like the Reverb issue is in the signal path because the idle points look pretty good on the driver and recovery stages. See if you can determine if either one is working by doing the listening tests above.

BTW, nice work on this! It is as others have said, it's a complex circuit, but proceeding carefully in a systematic way it is not impossible for a relative beginner. Note we headed-off a couple of problems along the way by using the modular build and test process. The layout is decent, but has a few problems, and some experience is required to spot them.

[Mousey Dung]

Woo hoo! Looking good there.

Soooooo relieved!!!

Seems like the Reverb issue is in the signal path because the idle points look pretty good on the driver and recovery stages. See if you can determine if either one is working by doing the listening tests above.

Will work on that now. Got mesmerized by the tone, rich harmonics and all the different possibilities of the amp.

BTW, nice work on this!

Thanks. I know there are lots of gaps in my knowledge, but I do have some good instincts, learn fast and know how to be systematic.

It is as others have said, it's a complex circuit, but proceeding carefully in a systematic way it is not impossible for a relative beginner. Note we headed-off a couple of problems along the way by using the modular build and test process. The layout is decent, but has a few problems, and some experience is required to spot them.

I really jumped in on the deep end there, didn't I? That's just the story of my life. But I'm glad I survived this. I couldn't have done it without your help!

[Mousey Dung]

Seems like the Reverb issue is in the signal path because the idle points look pretty good on the driver and recovery stages. See if you can determine if either one is working by doing the listening tests above.

Still no luck. The cable is a dual RCA with a ground wire sandwiched in the middle. I've connected red to red, white to white, and the ground to the chassis. I've put my finger on the RCA connections inside the reverb tank, and there's no buzz... done the sound test, no sound.

I'm now checking the signal path for short circuits. The green and black cables at the red RCA input on the chassis are shorted -- is that supposed to be like that?

[martin manning]

Green is the signal lead so it should only go to the center connector of the send jack. Black goes to the send jack's ground lug.

[vibratoking]

Martin, you're a Saint.

[jelle]

I was thinking the same thing about Martin.

[martin manning]

I'm now checking the signal path for short circuits. The green and black cables at the red RCA input on the chassis are shorted -- is that supposed to be like that?

Or maybe you're saying you meter from black to green and see a short? You should see a very small resistance there since it's just the secondary of the driver transformer, which is a relatively short piece of wire.

VK & Jelle- nah... I just can't resist a puzzle.

[stelligan]

I was thinking the same thing about everyone helping out!

A kit purchased from a commercial site. OP joins up for what seems like the sole purpose of getting help he can't get from seller. Posters patiently get him near the finish line in record time. Many of these accomplished builders could be at their benches building their own amps instead.

Here's hoping that OP sticks around after this to do a scratch build or something and is not just a drive by. I have for sure received more than I have given here. I stick around to learn and stick around because of the vibe of all you smart, helpful people.

Post is not meant as a slam to Brown Note or OP, more as kudos to the brotherhood and generosity here. GAWD, this forum is awesome