Shucks ! No luck
After completing the kit I got active "Power" indication and nothing else. Using the same source and coax that works perfectly with the Lexicon unit - no other LEDs would light. No sound but there was a slight hiss and some low 60 cycle shadow noise.
Things I checked:
1. 17.8 and 11.1 VAC to power terminals. (though rated 15/9 on label)
2. No temp beyond room temperatures on board or toroid.
3. No visible solder bridges.
4. 1.6 VDC across both audio out RCAs
Luckily, no other equipment was damaged, but turning up the volume pot on the MyRef Integrated amp caused both LM3886 to trigger their protection circuits. Going back to PC --> Lexicon --> Integrated Amp was fully functional again.
The only other possible mistake was initially not using the Euro-style terminal on the 15-0-15 power in. I made direct connections to the board. I don't know if that could cause a problem.
Please review the pics for anything I'm not seeing
After completing the kit I got active "Power" indication and nothing else. Using the same source and coax that works perfectly with the Lexicon unit - no other LEDs would light. No sound but there was a slight hiss and some low 60 cycle shadow noise.
Things I checked:
1. 17.8 and 11.1 VAC to power terminals. (though rated 15/9 on label)
2. No temp beyond room temperatures on board or toroid.
3. No visible solder bridges.
4. 1.6 VDC across both audio out RCAs
Luckily, no other equipment was damaged, but turning up the volume pot on the MyRef Integrated amp caused both LM3886 to trigger their protection circuits. Going back to PC --> Lexicon --> Integrated Amp was fully functional again.
The only other possible mistake was initially not using the Euro-style terminal on the 15-0-15 power in. I made direct connections to the board. I don't know if that could cause a problem.
Please review the pics for anything I'm not seeing
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Hi Bob,
I can't see obvious errors but the DC offset make me think of opamp's rails.
I would measure:
- analog AC rails vs ground
- DC entering the regulators
- DC leaving the regulators
- opamp rails
Attachments
A couple questions before I start poking around.
1. Which group is referred too as "digital" - which analog (123 vs ABC)?
2. What's the best spot to pick for ground to do the opamp readings?
3. Please confirm rails are picked up direcrly from legs of 15V chips - 1,2 & 3. ( just noticed one is L7912CV the other is L7612CV)
Please bear with my lack of confidence/knowledge in this area. Gives me the he-be-gee-bees
Remember - I'm an ears guy not a schematic scholar.
1. Which group is referred too as "digital" - which analog (123 vs ABC)?
2. What's the best spot to pick for ground to do the opamp readings?
3. Please confirm rails are picked up direcrly from legs of 15V chips - 1,2 & 3. ( just noticed one is L7912CV the other is L7612CV)
Please bear with my lack of confidence/knowledge in this area. Gives me the he-be-gee-bees
Remember - I'm an ears guy not a schematic scholar.Attachments
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Yes, there's a big difference, IMHO, otherwise why bother changing them...
Motorola are exactly the same part (On Semiconductors is the old Motorola Semiconductors Division...) so the MC7912CT are OK.
TI parts are like the others so you should order some On Semi MC7812
The analog section is the one where I put values in the picture I've attahced in my previous post (7812, 7912, LM1117-5)
The nearest will do (see where I've indicated 0V)
No, only 2 and 3 are the 15V analog regs one posistive (7812) one negative (7912).
Pay attention! 7812 and 7912 have different pinout!! See my picture for reference.
Dario
I'd say it's a 7812(bad stamp on the 8) but you have the 79 and 78 in the wrong positions.
See attachment:
I'm afraid you swapped regs...
Possibly also LM117-5 and LM117-3 are burnt, maybe the DAC chip...
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ANNOUNCEMENT ! New restaurant in Michigan - Featuring sausage and fried chips. Come one, come all.
Dario and Fan are correct as the readings show. I remember separating out the 9cv from the 12 cvs but never took a close look at the board markings. Details, details, details.
So I need to order:
1 LM812CV
1 AK4393
2 LM117-3.3v
1 LM117-5v
Anything else that might be suspect ?
Hopefully my mistake will help others avoid the same.
Dario and Fan are correct as the readings show. I remember separating out the 9cv from the 12 cvs but never took a close look at the board markings. Details, details, details.
So I need to order:
1 LM812CV
1 AK4393
2 LM117-3.3v
1 LM117-5v
Anything else that might be suspect ?
Hopefully my mistake will help others avoid the same.
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There is a slim chance that you could get away with putting new regulators in you get these from radio shack tomorrow.
Do you have the ability to solder a new AK chip onto the board?
Try changing the 12V regs first, you might just get lucky.
if not get a new board and save yourself the grief.
Do you have the ability to solder a new AK chip onto the board?
Try changing the 12V regs first, you might just get lucky.
if not get a new board and save yourself the grief.
Hi guys, Glad to know I might be able to get some items from RS. Yes, I have soldered several surface mount chips successfully. I had planned to re-populate the board with Dario's upgrades so this will just be a little more practice. I've had good luck with a hot air gun for desoldering.
Thanks All.
I've had good luck with a hot air gun for desoldering.Thanks All.
Order an AKM4396, much better.
Also electrolythic caps on rails path can be blown.
But first replace the two LM7812/LM7912, maybe the rest is good.