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A Very Compact Hybrid Amp - Page 114

post #1696 of 2213
Quote:
Originally Posted by runeight View Post
If you're not having problems there is no need to make this change.
BTW, the symptom I had was, 30 secs after pwr-on, e12 would go "green" for a minute or so then drop out ("red") until CTH was unplugged & allowed to cool. Both input & output of 24V reg measured below normal when exhibiting the condition. CTH had 50 -> 100 hrs on it & was not as well-ventilated as SCL kits. My original CTH (avatar) w/far more hrs has not exhibited this problem.
One of sachu's CTHs developed similar/related issue w/Q1P.

So if a problematic CTH's 24V supply reads low, suspect Q1P & replace w/BC337.
post #1697 of 2213

Progress so far

Quote:
Originally Posted by runeight View Post
It IS possible depending on how different the hfe in the class 40 device is from the other class 25 output transistor in the buffer. It should be done anyway so that, if there is still a problem, we can elminate this as a source of the problem.

This eventually has to work. Don't give up!!!
Well I have good news and bad news
Repacing q8r has corrected the voltage problem.The voltage at r18r is now 12V approx and all other voltages ok

The problem now is that even though the LED is turning green there is no switching noise from the relay and no voltage on OR and OL

But at leaast we are making progress
post #1698 of 2213
Quote:
Originally Posted by Ged View Post
Well I have good news and bad news
Repacing q8r has corrected the voltage problem.The voltage at r18r is now 12V approx and all other voltages ok

The problem now is that even though the LED is turning green there is no switching noise from the relay and no voltage on OR and OL

But at leaast we are making progress
Can you check the voltages at the ionput and output or the 7824 voltage regulator. Be careful not to short anything there.
post #1699 of 2213
I am sorry i do not understand !
post #1700 of 2213
Can you measure the voltage between both the outer edge pins of the regulator ..the ICP one with the heatsink on it.

PLace the black probe on SG and the red probe on the each of the outer edges of the regulator and measure the voltage please.
post #1701 of 2213
the voltages are 24 and 34 volts
post #1702 of 2213
Quote:
Originally Posted by Ged View Post
The problem now is that even though the LED is turning green there is no switching noise from the relay and no voltage on OR and OL
Never have seen this... IOW whenever LED goes from RED -> GREEN the relay kicks.

The the modified e12 circuit schem is here.
Perhaps runeight can chime in, but don't see many ways for CTH to go green but relay not to latch. Especially as you said this CTH worked fine at one point....
post #1703 of 2213
I wonder if thers another problem I was quite surpised myself but could it be as simple as a faulty relay. the main reason i am surprised is that i heard it latch before

thanks for the blob of solder trick it works great
post #1704 of 2213
Thread Starter 
If the LEDs change then there is voltage being applied to the pads of the relay coil.

Ged it might be a good idea to measure this. The two power pins are the relay pins towards the front edge of the board. What is the voltage between these two point when the lights are in the two different conditions?

If there is voltage here then the relay is either bad or has a bad solder joint.

We're getting closer.
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 #1705 of 2213
Thread Starter 
Quote:
Originally Posted by Billyk View Post
OK to start I have a more sane supply. 24.4VAC unloaded. It is spec'd at 20v 1amp. Things are cooler for sure I can hold my finger on the reg heatsink now and it's moderately hot just a bit more than warm, so I think things are good there. I changed the tube out, the plate voltages changed from pin1 90v pin 6 81.6v to what I put down below. I also changed the output jack and wiring. I know I changed a lot at once, not the best for troubleshooting I cannot recreate the bass distortion and e-12 activation... Hopefully things are better!!
My measurements as requested.
Tube:
1- 78
2- 0
3- 1.7
4- 6.0
5- 0
6- 78.4
7- 0
8- 1.6
9- 0

IC1
1- 7.5
2- 11.9
3- 11.9
4- 0
5- 11.9
6- 11.9
7- 5.4
8- 24

Tube = 6BQ7A

Billyk these voltage are all well within spec. Are you having any further problems?
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 #1706 of 2213
Quote:
Originally Posted by runeight View Post
If the LEDs change then there is voltage being applied to the pads of the relay coil.

Ged it might be a good idea to measure this. The two power pins are the relay pins towards the front edge of the board. What is the voltage between these two point when the lights are in the two different conditions?

If there is voltage here then the relay is either bad or has a bad solder joint.

We're getting closer.
Cant get a reading when LED red
When green = 11.5v
Cleaned and reflowed solder joints no difference
post #1707 of 2213
Thread Starter 
OK. This at least makes sense and doing the right thing.

Need another test.

Turn off the power and bleed down the 24V PS until it is 0V. If you need to use a 1k resistor across C1P to bleed this all the way down.

The measure the resistance between the same two pads on the relay where you measured the voltage. It should be about 1100 ohms.
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 #1708 of 2213
The reading for the above is 608ohms
post #1709 of 2213
Thread Starter 
I'm sorry. I forgot to ask that you measure with both polarities of the meter. This will test both the diode and the coil.
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 #1710 of 2213
Readings are 1000ohms and 608ohms
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