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A Very Compact Hybrid Amp - Page 73

post #1081 of 2213
Yes, no thread hijacking

I'm kinda bummed H-wize is down and there's no access to the EHHA thread. Love my CTH's but giving this a go as well, need to decide active ground or fully balanced... Oh, I see Smeggy just started a thread here!

Ok, back to our regularly schedled thread
post #1082 of 2213
I'm starting to think the Headwize forums will never make it back.
post #1083 of 2213
Looks like we have yet anotehr CTH that lives..

The proto board is up and runnig...

Ther emight be a channel imbalnce (one of the buffer transistors maybe on the right channel)

No smoke thus far.
Check back later.

Got one more CTh build for this weekend to come.

Cheers,
Sachu
post #1084 of 2213
Great news!

Let's hope it stays working this time
Now, get over to the EHHA thread, I need help
post #1085 of 2213
holland.


I just checked the current flowing through the CRD......

bang on 2ma.

volatge at pine 1 = 101v.

we can rule out the CRD as a starter, we can rule out the opamp.

any more guesses?
post #1086 of 2213
Thread Starter 
There are only four possiblities:

1. There is something wrong with the traces in the servo circuit.
2. You have a wrong/bad/mis-oriented component in the servo
3. The grid of the triode is not grounded through the leak resistor
4. You are in the twilight zone

I don't know which it is.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1087 of 2213
4, 100%
post #1088 of 2213
ignore me - a hypothesis quelled with logical thought.
post #1089 of 2213
Thread Starter 
probably not. if the volume control is set to zero the resistance across R1L will be zero ohms. even so, this value is ok because it means that the grid is grounded. which is where it needs to be.

there MUST be something wrong with the servo components if the grid is grounded. or the traces are bad.

is the opamp socket in the correct orientation?

Edit: Nevermind.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1090 of 2213
runeight, the vol was at minimum so its ok.

I may end up removing all the omponents in the servo and starting again. Its just about got me completely stumped.
post #1091 of 2213
Thread Starter 
same here. i really don't know what the deal is.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1092 of 2213
I'm lost as well.

1) You've also stated that the resistors are in the proper places, looking at the initial voltages, I would tend to agree.

2) With the opamp removed, everything is working as it should. Opamp is known to be good. That leaves component and traces.

Take another go through your pics, I guess. Nothing is jumping out.
post #1093 of 2213
I'll give it a going over tomorrow, I'll take out all the components, test them out of circuit, i think replacing the caps in the servo is probably sensible.

bizarre one!
post #1094 of 2213
moderator, can you forgive me swearing.....

thank the F#####ng lord.

all sorted. finally i tracked it down to a grounded opamp pin that should not have been grounded.

its now making good music, but there is a fair bit of ground hum, particularly when i am near the vol knob.

big thanks to holland and alex for the persistence

do people find the 24v reg runs pretty hot?
post #1095 of 2213
Congrats!

That thing with the heatsink? If so, yeah. Toasty little sucker. I was even thinking of adding a bigger sink to it.
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