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Hi all,
I cannot get my retro up and running...
I got the "OP-amps premounted" version, soldered the other parts, added an LCBPS and configured it to output 12V (with 2x12V transformer)...
Just to test I powered one board only from LCBPS, connected IN+ to in-rca center, GND and IN- to in-rca border and got the OUT+ to out-rca center and the other free GND to out-rca border. I know that this is not the right config for BAL/SE converrsion (I also got the Venus EZ waiting to be plugged) but as I said it was for testing only...
I connected one channel for my turntable (Thorens TD126 w/ stanton cartridge) and the output channel to my preamp (old SAE 2100L)...
I got no hum, buzz or anything like that but I also got NO sound... Only an irritating click when I change the position on the stepped volume pot of the SAE!!!
Is there anything I should check first...? Any help will be appreciated!
Thanks in advance
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There may be some (should be small) common mode DC at the output, you may need an output cap in the configuration you are using.
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Sorry for my newbie questions but what specs should these cap have?
I think I have some spares from an opus I built some time ago and since I used transformers I have them sitting... They are some Elna 22uF 25V...
Will they be OK?
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Also, as a newbie to this stuff, I must have made a big mistake because without any inputs or outputs connected on the rca I get ridiculously large DC values on them... 8,9 on in and 11,1 on out...!!!!
Is there something I should test more specifically (any test points I could use)?
Thanks in advance
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That is obviously wrong.
Please check any DC on inputs, I assume the first opamp failed.
If you got any DC on inputs, you should not connect the cartridge.
If the assembling is correct, you should see zero DC in inputs and outputs (a few mV possible on outputs).
These are good testing points.
The next could be AC measurement on outputs while touching (by your finger) the inputs - there should be some "activity".
After that connect the cartridge and the amplifier.
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Buffalo24+Tubes (XLR), Retro with MC LO |
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Thanks for the response....
Yesterday, after a more thorough look (and check) I think one problem was at the power supply board... I changed to a second LCBPS I had available and the measurement between IN+ and IN- is 0... The output though gives me some strange measurements, OUT- and OUT are around 0,4 but OUT- and GND or OUT+ and GND give large values (around 8 to 11)...
I will check later also for AC but I think that it is OK...
The Opamps were premounted on the boards so, unless I made a great mistake and fried them, I think they are OK.
Am I measuring correct (I mean the IN/OUT combinations) or I should I try to measure something else...?
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Please measure all in/out/plus/minus to GND.
Do you have a chance to check the temperature of the opamps while powered ? |
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By measuring to gnd all give large values of DC... The temp also on all opamps seems to be extremely high even after a few seconds of operation (I cannot touch them)...
Is that correct? The ones on the ventus ez have low temp (cold)...
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Are you able to measure current level on power supply lines ? I cannot recall exact value but it should not more than 50mA per rail per board.
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Well it is over 50mA...
It is 78mA on V- rail and 125mA on V+ rail...
I also remember something 50mA from another thread here...
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Would you connect all inputs to GND and verify the effect ?
(DC on output, IC temperature, current level) |
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yes, do not short to GND the outpus, in case of such a need use resistor, 10k or above |
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All right... It seems to me that something is wrong with my V+ rail and OUT+...
With grounded IN- / IN+ I got OUT- 4V, OUT+ 11V!!!
As far as current levels I got V- 55mV and V+ around 160 to 190mV!!!!
And all these happens on both boards... Could this indicate something wrong with the LCBPS?
If I made a mistake I think it will be difficult to make it on both boards... Unless my being a newbie is the actual cause...
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a picture could help here,
are you able to post two photos ?
(both sides) |
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Twisted Boys (or Girls) made a mistake for you.
OPA1642 should be in the middle, and OPA1632 should be by the input/output connectors
(true if ICs were premounted)
Now - if you are lucky and ICs are not fried - you can exchange these and the board can start.
If you cannot do it by yourself ask any mobile phones (or game console) service points to do the swap.
Should not cost more than 5-10 Eur, 10 minutes task. |
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Excellent... :-(
And I was wondering what I have done wrong with the simplest soldering in the world... ;-)
Thanks a lot for your time... I owe you one...
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Originally Posted by: benpe  Twisted Boys (or Girls) made a mistake for you.
OPA1642 should be in the middle, and OPA1632 should be by the input/output connectors. Well, since there is only one person building and shipping stuff, I guess it's pretty easy to figure out who made the mistake (me)  If you need help swapping them, or if you have any issues, please let me know and I will get things straightened out for you.
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There is one more issue - as the input IC is mounted 1632, so you got two 1632 and one 1642, should we exactly the other way around.
You need to get extra 1642 and place it correctly.
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