Hertz HP1D problems

[Perry Babin]

Do you have the service manual for this amp (I don't have it)?

It appears that they changed the pin configuration on the 3640 board.

 

[ViNzZz]

No, I haven't. There only pin twist, the board is the same. I can get a photo if you want..

 

[ViNzZz]

With rca jack in, if I try to connect oscilloscope ground to 12 volt regulator's ground there is very very high current from this connection (there are sparks on connector!!!). Now tl074 is died. What is it????? I've never seen something like this...

 

[ultra]

you should ground your scope to the power supply ground or to the secondary ground.
You saw sparks because you tried to ground V- minus 12V.
Please be careful with that.

 

[ViNzZz]

Only connecting oscilloscope ground? I don't knew that. Thanks a lot

 

[ViNzZz]

Signal dies on R34m, near IC11A1. Now I try to found why. Any ideas?

EDIT: I see sine wave on IC11A1 pin1 (output) but nothing on pin 2,3. Why? I don't understand the circuit

 

[ViNzZz]

There was a bad connection. I see audio on pin4 of the center connector of driver board. What I have to check?

 

[ViNzZz]

I see square wave @50hz on the driver board. I can't see from where it comes, but it's a perfect square wave, so I think it's coming out from lm211. I should see square wave on gate legs of the outputs (with outputs out of the board)?

 

[ViNzZz]

I see square wave on gate leg of only 2 outputs. Should I have also square wave on other legs?

 

[Perry Babin]

Are you driving a 50Hz sine wave into the amp?

 

[ViNzZz]

Yes. The square wave is at -85 Vdc (on Q208 gate pad),I think it's ok. But on the remaining gate pad there is 0 Vdc or rail voltage. Is it correct or no?

 

[ViNzZz]

I found pin 3 of IR21844 on the right disconnected. Can this be the cause of non seeing square wave on the other pads?

EDIT:On 4 of 8 gate pad I see square wave at -85 Vdc. On the other 4 I see only a little Spike (about 200 mV). It's Correct (outputs are out of the board)

 

[Perry Babin]

The high-side is more difficult to check. Try grounding leg 3 of the high-side FETs (those with +85 on the center leg). Be VERY careful not to short the center leg to ground.

Does that allow you to see the driver signal on leg 1 of the high-side FETs?

 

[ViNzZz]

I installed mosfet, I see also the high side. Sound is distorted. What can be the cause?



EDIT: Ihear crapping, scratching or something like this and when I hear this the square wave is distorted. The scratching seems to be near output inductor

 

[Perry Babin]

Is the audio signal clean at the last op-amp before the driver board?

'Distorted' isn't very descriptive. Post a photo of the output with a 100Hz sine wave.

 

[ViNzZz]

Seems to work fine now. Maybe are relais or pot. I try to get new ones.

I've installed only 4 fet (1 for each HI and LO side) to run a test. 1 ohm load can be dangerous? I wanted to test it at low-middle volume.

 

[luigidedom]

hi could you perhaps tell me what is q3 on driver board

 

[ViNzZz]

Q3 is a MAX

 

[luigidedom]

Thanx

 

[ViNzZz]

Noise is come back, also without RCA jack insert. Sometimes is very very high and the amp goes into protect. Sometimes (when is very very high) I hear it coming from relais or capacitors. What can be?

This is when is low....
https://www.youtube.com/watch?v=QinL2gQ3QsA&list=UULCD3dzxU85s74safPk3usg