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A Very Compact Hybrid Amp - Page 119

post #1771 of 2213
Does anyone happen to have an extra BC337, for the new Q1P that they could spare?
I placed a parts order back in the middle of August for my 2nd CTH and just discovered the change on Alex's site.
Thanks..
post #1772 of 2213
Um, I might have a few... Let me know what you need...
post #1773 of 2213
Bill,
I only need one for now.. unless I blow a few things up.. Trying to be extra careful this time.
You should have my address from a previous order (I ordered a board and the short perf top). PM me with your costs and I'll get it off to you.
Thanks!
post #1774 of 2213
i have a bunch to spare..PM me and I'll send it off to you tomorrow..Bill's busy with something that he needs to send to me first
post #1775 of 2213
Fair enough Sachu - you'll be getting yours soon. Let me know if I can replace the 337's you send to Mr Slim. I have a kajillion or so...
post #1776 of 2213
I am having a weird problem with a CTH build.

The relay keeps tripping on and off and then stays off for extended period of time and then randomly starts switching back and forth again before settling to the Off position..

All voltages except for OL-> SG and OR ->SG check out.

I tried swapping the opamps out on the buffer and the E12 just to rule them out even though i was getting the proper voltage readings on the E12 opamp (Pins 1, 2 and 6 were at 12 volts)

The problem I think could be with a possibly faulty relay or the coil voltage not being right.

Relay pins 1-> SG and 12-> SG read close to 24 volts..this has to be wrong as the coil nominal voltage is supposed ot be 12 volts at least for the relay to be actuated.. Right?
Pins 3,4,9 and 10 all read 12 volts with respect to SG.


Here is the relay part

Appreciate any input.
post #1777 of 2213
here's my input, yours is doing exactly what mine is doing. Aside from those suspected blown trannies, this is exactly why we went through the E12 bypass surgery on mine. Sounds like exactly the same thing. So if you do figure it out, I would love to know.
post #1778 of 2213
Quote:
Originally Posted by sachu View Post
The relay keeps tripping on and off and then stays off for extended period of time and then randomly starts switching back and forth again before settling to the Off position..
<snip>
The problem I think could be with a possibly faulty relay or the coil voltage not being right.
First thing to check is to see if what is happening is that your e12 is doing its job.... IOW, are its trips due to DC offset?

AFAIR think CTH e12 trips when offset gets like 50mv->100mv on a channel. I'd setup 2 DMMs on the L&R channel *input* to the relay & see what's happening there.

If its not offset thats causes e12 relay drops and you suspect the relay itself or its voltage drive levels see a few pages back where runeight & I tried diagnosing that in a build...
post #1779 of 2213
Thread Starter 
Quote:
Originally Posted by sachu View Post
I am having a weird problem with a CTH build.

The relay keeps tripping on and off and then stays off for extended period of time and then randomly starts switching back and forth again before settling to the Off position..

All voltages except for OL-> SG and OR ->SG check out.

I tried swapping the opamps out on the buffer and the E12 just to rule them out even though i was getting the proper voltage readings on the E12 opamp (Pins 1, 2 and 6 were at 12 volts)

The problem I think could be with a possibly faulty relay or the coil voltage not being right.

Relay pins 1-> SG and 12-> SG read close to 24 volts..this has to be wrong as the coil nominal voltage is supposed ot be 12 volts at least for the relay to be actuated.. Right?
Pins 3,4,9 and 10 all read 12 volts with respect to SG.


Here is the relay part

Appreciate any input.
The voltages you're measuring are correct for a relay that is not turned on. 3/4 & 9/10 are the NC terminals, connected when the relay is off. 4 and 9 are the outputs from the buffers. They should be at 12V to SG as you measured. 1 and 12 are at 24V making the relay off.

However, if you are measuring when the relay should be on then there is definitely a problem in the e12 circuitry.

We desenstized the e12 to trip at about 180mV and we made it slower than the stock version.

So, if you measure R18R and R18L with respect to OG and these voltages are less than 180mV then the relay should be on. These are the same as pins 4 and 9 on the relay.

If you can make these last two measurements then we will know something about what condition the e12 is in.

EDIT: I swapped 9 & 10 in the discussion. I fixed that.
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 #1780 of 2213
Alex, I tried measuring the DC offset.

It was less than 5mV between pins 4 -> OG and pin 9 -> OG.

I replaced the relay and tried..no god.

I replaced D1E and D2E and still no good.

Verified all resistors and transistors to be in their place.

Where do we go from here?
post #1781 of 2213
Thread Starter 
It would seem that the only devices left are the transistors.

You might start with the MPSA14.
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 #1782 of 2213
Still the same..I suppose that menas I replace the other 4 transistors and see what happens.
post #1783 of 2213
bah weak sauce...replaced all the transistors in the E12 and still the same while the offset is well below the threshold.
post #1784 of 2213
Thread Starter 
There are not many things left to go wrong.

Check the orientation of D3E. Maybe it's backwards.

If not, then measure all pins of the opamp. Make sure it is in with the right orientation. Let us know these voltages.

If these are all ok remove one lead of R6E to disconnect the lights.

Still not working? Then remove the relay and check the coil resistance between 1 & 12.
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 #1785 of 2213
D3E is okay.

removing one lead of R6E made no difference..the relay kept switching back and forth till it settled down to Off position.

Opamp is in correct position.

PIns and voltages
1-> 0.203V
2-> 12.03V
3-> 12.03V
4-> 0V
5-> 0.203V
6-> varies between 11.95-12.17V constantly varying even when relay is in off position.
7-> 24.06V
8-> 0V

Let me know if I need to remove the relay and measure the coil resistance..I did replace the relay with a new one when i did the last series of tests.
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