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A Very Compact Hybrid Amp - Page 50

post #736 of 2213
Quote:
Originally Posted by nux View Post
Only problem is I'd need to get a 1.5" hole on the top, most step bits don't go that high. I'll go buy a metal hole saw tomorrow and see how I go.
This: STEP DRILL BIT 1/4 TO 1-3/8" TITANIUM BITS TOOLS - eBay (item 250404606464 end time Apr-12-09 20:34:11 PDT)

goes up to 1 3/8", which is plenty large enough for the tubes used in the CTH.
In fact, it's just the right size to use a ring from a tube protector to "finish" it up, like the last pic here:
http://www.head-fi.org/forums/5527658-post438.html
post #737 of 2213
Quote:
Originally Posted by Coreyk78 View Post
That way I can't screw up and have the hole a little off center, you know, one of those things that most other people wouldn't notice, but you know it's there so you can't help staring at it?
As there will always be variations with drills and even tube socket center soldering - The hole is drilled a little larger than the bushing diameter so there's a little 'float' - this way you can have that 'exactly centered' look.
post #738 of 2213
Arghh... I cased up my CTH and now the e12 is not opening up. The led stays red. My voltages test out ok- TB+ 103v, outputs are all around 12v, pins 1 and 6 are near 80v, the tube lights up, nothing is seemingly hot or smoking. I checked the wiring on the pot and jacks and it is all ok. I guess I damaged something in the e12? Any advice on how to troubleshoot this?
post #739 of 2213
Where did you wire SG?
post #740 of 2213
It's bolted to the case. Continuity seems to check out ok as well.
post #741 of 2213
Quote:
Originally Posted by nux View Post
Only problem is I'd need to get a 1.5" hole on the top, most step bits don't go that high. I'll go buy a metal hole saw tomorrow and see how I go.
DOn't go the hole saw route...its a disaster I tell you.

Just get a round file, drill out a hole big enough to put it through and then file away.
The hole saw will almost surely mess things up for you.

Congrats on your first build...That was really fast considering the components had to be shipped to australia..
post #742 of 2213
I did some more testing. With a tube in, I am getting 11.9v on the OL and OG and 0v on OR. What did I do? This is frustrating.

I guess I shorted OL to OG somehow.
post #743 of 2213
Quote:
Originally Posted by tacitapproval View Post
I did some more testing. With a tube in, I am getting 11.9v on the OL and OG and 0v on OR. What did I do? This is frustrating.

I guess I shorted OL to OG somehow.
take off the tube, meaure OL to SG and OR to SG and report back the values.
Can you tell me what resistors you have at R1E, R2E and R4E?

Also values of R14L/R and R15L/R
post #744 of 2213
I fixed the wiring, now I am getting 12v on OG and 0v on OL and OR without a tube.

I have all BOM values at those positions. Keep in mind this was working fine until I did something boneheaded during the casing.
post #745 of 2213
So I guess I killed either the opamps or the buffer transistors?
post #746 of 2213
Quote:
Originally Posted by tacitapproval View Post
I fixed the wiring, now I am getting 12v on OG and 0v on OL and OR without a tube.

I have all BOM values at those positions. Keep in mind this was working fine until I did something boneheaded during the casing.
And what was this 'boneheaded' move?

if you have 33k in R1E and R2E and 2k in R4E, 15K each in R14 and R15 which are BOM values, we can move on to other things..

getting 0V on OL and OR means that the relay is not tripping.

Try changing the opamp on the E12 along with the opamps for the input buffers..which is ICL and ICR. Then give it a shot and report back.

Also what are you getting at Tb+ and at the plates of the tube?

Cheers,
Sachu
post #747 of 2213
I'm not sure what the fatal bonehead move was. Would shorting OG and OL damage components?

Unfortunately, I don't have anymore TL081s.
post #748 of 2213
Thread Starter 
Shorting OG to OL might do damage, but there are other suspects first.

Change out the TL082. It could just be the opamp. If you don't have any more of these you can use OPA2134 or anything similar.

If this doesn't fix the problem then we have other issues.

However, Sachu is correct, if the e12 is not tripping to green then OL and OR can be anything. We'll have to measure inside the circuit. But try the opamp first.
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 #749 of 2213
I swapped TL082 for a 2227, but still no green light.
post #750 of 2213
Thread Starter 
OK. Is the 2227 a jfet input opamp? I have forgotten.

Next text is to meaure all of the pins on the buffer opamp with respect to SG and report back. And you said that OG is 12V (or very close)?
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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