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A Very Compact Hybrid Amp - Page 101

post #1501 of 2201
6/6/09 at 12:02am
lgn - If I understand you correctly, your e12 (and amp) is functioning normally but your e12 LED isn't working?

This could be bad transistors (Q4,5E) in the led indicator section of the12 (I had a similar problem in my proto build...)
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post #1502 of 2201
6/6/09 at 12:15am
That definitely could be happening. I have ran my amp for more than a week on the wrong configuration (R8E and R9E) swapped and that might have blown the transistor. Or I might have just broke one of the pins when I was fixing it a couple hours ago. Either way, the amp is working fine so I am going to live with this lively orange color for now. Thanks for all your help, Bill.
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post #1503 of 2201
6/9/09 at 8:48am
I exchanged Q8R and Q8L, but still no change.
How can I test if D2R is not working correct? Diode test isn't working here, is it?
Greetz Ava

Please help! pleeeeeeaaseee...
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post #1504 of 2201
6/9/09 at 10:47am
Ynis - AFAIR Holland & runeight have been very good at pinning down issues in CTH to particular part(s), but I think they may be unavailable ATM.

Having had issues way back in my proto PCB build, and having incrementally replaced targeted components to no avail, as the parts are available & inexpensive in the US I choose the shotgun approach. I needed the amp going for a meet & couldn't fiddle around.

It seems to me one buffer is locking up & dumping voltage directly to output.

Assuming you've assured all the correct components were installed in the correct places w/the correct orientation & there are no shorts, just to be clear, what exactly are your measurements for all of the following:

# Measure between OG and SG. This should be very close to 12V. If it's not there might be a problem with the TLE2426 or with one of the devices in the rail splitter.

# If the OG measurement is good, measure OL and OR (with respect to SG) . They should also be very close to the voltage at OG. If they are the buffers and splitter are working.

# If OL and OR are not close to OG (>50mV), then either the buffer opamp is not working or one or more of the buffer BJTs are dead (or the wrong hfe class - not possible if you've Bill's kit). IOW, what are your OL <-> OG & OR <-> OG voltage measurements?
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post #1505 of 2201
6/9/09 at 12:18pm
Ynis - If Memory Serves, there was a discussion about CRD function around a problem Adamus had ~post#1028. I just did a quick search but don't remember the exact symptoms or if they were similar to yours, but you might review the posts immediately before and after...
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post #1506 of 2201
6/9/09 at 1:19pm
Quote:
Originally Posted by cfcubed View Post
Ynis - AFAIR Holland & runeight have been very good at pinning down issues in CTH to particular part(s), but I think they may be unavailable ATM.

Having had issues way back in my proto PCB build, and having incrementally replaced targeted components to no avail, as the parts are available & inexpensive in the US I choose the shotgun approach. I needed the amp going for a meet & couldn't fiddle around.

It seems to me one buffer is locking up & dumping voltage directly to output.

Assuming you've assured all the correct components were installed in the correct places w/the correct orientation & there are no shorts, just to be clear, what exactly are your measurements for all of the following:

# Measure between OG and SG. This should be very close to 12V. If it's not there might be a problem with the TLE2426 or with one of the devices in the rail splitter.

# If the OG measurement is good, measure OL and OR (with respect to SG) . They should also be very close to the voltage at OG. If they are the buffers and splitter are working.

# If OL and OR are not close to OG (>50mV), then either the buffer opamp is not working or one or more of the buffer BJTs are dead (or the wrong hfe class - not possible if you've Bill's kit). IOW, what are your OL <-> OG & OR <-> OG voltage measurements?
Well I meassured, and OG-SG meassures 12.02V.
OL-SG meassures 4.6mV (12.01V before the E12)
OR-SG meassures 1.9mV (23.14V before the E12)
OL-OG meassures 0mV (but oszialates between 29.1mV and -28.8mV before the E12)
and OR-OG meassures 0mV (11.14V before the E12)

Geertz Ava

btw thank you very much for taking a n interest in my problem Cfcubed!!
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post #1507 of 2201
6/9/09 at 1:19pm
My issue was high voltage at pin 1, i.e the servo circuit not working, nothing like this i am afraid. In the end the CRD was ok but there was a bridge trace on the opamp pin to ground.
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post #1508 of 2201
6/9/09 at 1:26pm
Quote:
Originally Posted by Ynis Avalach View Post
OR-OG meassures 0mV (11.14V before the E12)
The 0mv is because the relay/e12 is not engaging due to the actual OR-OG offset of 11.14V. BTW, the whole reason this amp has built-in e12 is exactly for this protection.

So I think we can say with some certainty its a problem in your Right Output Buffer. As your Q8R vs Q8L indicate. Exactly what is wrong will need to be thought about. Let me think

Edit: Sorry to ask this (again) & not sure how much below you've already done, but could you *very* carefully review the Right OB components & check above & under PCB for any shorts?
And possibly (carefully) re-flow the solder on all the Right OB connections then re-check for shorts. Remove TL082 IC from buffer when you are re-flowing the socket's contacts.

If this does not solve it, consider swapping Right & Left TL082 ICs & see if OL / OG pre-relay goes to 11.XX volts. To see if its the opamp. If all this does not change/fix OR - OG I'd personally replace all "sand" in Right OB (TO92s + diodes), but that's not the smartest approach
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post #1509 of 2201
6/10/09 at 9:39am
Yippie....It works!!!!
Ok my fault!
I mounted Blackgates 10µF 50V for C5L and C5R and it seemed that C5R wasn't really ok. Have to check it now it's off board.
E12 relay engaged, hope to hear music soon.
Thank you very much Cfcubed!
Now that I have a working BoM I will slowly replace the things I wanted to replace.
And of course enjoy the music!
Greetz Ava
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post #1510 of 2201
6/10/09 at 9:55am
Oh my God beautiful! WOW!!!
Groovy, aggressive, pure energy, I can't take my crappy hd595 off (Ipod headphone out, not cased yet).
Thank You Alex! Thank you design team you did a wonderful job in creating this beautiful sounding amp!
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post #1511 of 2201
6/10/09 at 10:27am
Quote:
Originally Posted by Ynis Avalach View Post
Oh my God beautiful! WOW!!!
Groovy, aggressive, pure energy, I can't take my crappy hd595 off (Ipod headphone out, not cased yet).
Thank You Alex! Thank you design team you did a wonderful job in creating this beautiful sounding amp!
Hey great to hear all is well... Although this sophisticated design can be a bit tricky to debug think all CTHs are alive & well now

Quote:
Originally Posted by wiatrob View Post
As for under-heated tubes - 7DJ8s can be added to the list as well.
Silent @ zero volume with the 330uH and very nice sounding...
Quote:
Originally Posted by Forte View Post
Talking of underheated tubes, got what was supposed to be two 6FQ7/6CG7 tubes from eBay today. One is fine, but the second is a 8FQ7/8CG7(8.4V heater), was going to return it for a refund but after reading your post plugged it in and it sounds great even at only 6.3V! Have only had a short listen today but the 6CG7 sounds fantastic, one of my favorite tubes already.
Pretty obvious but been meaning to say that, because of the CTH's innovative heater supply, it would be trivial to support pretty much any heater voltages... Just use National's Simple tools to calculate desired (parallel) values for R1H/R3H and use a SP3T or SP4T heater switch among the various R3H values (6.3v, 7v, 8.4v, 12.6v)...
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post #1512 of 2201
6/10/09 at 11:25am
Glad to read that you figured it out Ynis and that your loving the sound. Just wait until you start rolling tubes...

Quote:
Originally Posted by cfcubed View Post
Pretty obvious but been meaning to say that, because of the CTH's innovative heater supply, it would be trivial to support pretty much any heater voltages... Just use National's Simple tools to calculate desired (parallel) values for R1H/R3H and use a SP3T or SP4T heater switch among the various R3H values (6.3v, 7v, 8.4v, 12.6v)...
Sounds like a great feature for CTH II.
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post #1513 of 2201
6/10/09 at 12:42pm
Quote:
Originally Posted by TimJo View Post
Glad to read that you figured it out Ynis and that your loving the sound. Just wait until you start rolling tubes...
I've already got 12BH7, EH ECC82 Gold, JAN 5814A, JAN 6922, Sovtek 6N1P and a Tungsram ECC82 waiting^^.
Thank you
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post #1514 of 2201
6/10/09 at 3:17pm
Excellent news Ynis, glad your working!

It has almost the perfect signature for me with the right tubes and it's a damn fine amp.
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post #1515 of 2201
6/13/09 at 6:00am
I'm having an issue with a Amperex 6DJ8 tube in my CTH.

It sounds great for about 20 minutes and then one of the channels goes bad. It gets quiet and distorted.
The tube also seems to get really hot (I know you're thinking I'm accidentally giving it 12.6 V - I even checked and it is definitely 6.3V)

Has anyone else experienced this? Is the tube dying?
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