Atomic AT-5000.1D

[mike49504]

I got this in for repair.. The output driverboard is brand new.. Also all of the outputs and power supply fets are also brand new..

Amp still has no output..

Heres a pic of the Output driverboard..

Heres the voltages i have on the pins of the driverboard ..

Any ideas?


Pin 1:-161.5
Pin 2:-162.0
Pin 3:-161.6
Pin 4:1.66
Pin 5:1.66
Pin 6:-161.1
Pin 7:1.66
Pin 8:1.66
Pin 9:-162.2
Pin 10:-162.2
Pin 11:-162.2
Pin 12:1.27
Pin 13:16.52
Pin 14:6.62
Pin 15:1.67
Pin 16:1.66
Pin 17:-3.20
Pin 18:2.05
Pin 19:-162.1
Pin 20:-162.0
Pin 21:-161.8
Pin 22:-161.4
Pin 23:1.66
Pin 24:1.66
Pin 25:-161.3
Pin 26:1.66
Pin 27:1.45
Pin 28:-162.0
Pin 29:-162.0

 

[mike49504]

Ok think i found 1 problem but not sure whats causing it..

On all of the TL072CN's i get voltage on the output pins..

Heres what i get on all of them..

Pin 1:1.52
Pin 2:1.66
Pin 3:1.63
Pin 4:-13.18
Pin 5:1.67
Pin 6:1.67
Pin 7:1.67
Pin 8:16.56



Pin 8 is 16 volts shouldnt that be 15 volts??
Pin 1-7 shouldnt they be at 0 volts??

Any ideas??

 

[Perry Babin]

The 16v isn't a real concern.

The op-amp seems to be working properly since the inverting and non-inverting inputs are essentially the same.

Have you checked all of the regulators in this amp? The ones feeding the driver board don't appear to be producing the correct voltage (from what little I know about this amp).

 

[mike49504]

Should i be using amps ground terminal or secondary center tap as reference??

 

[Perry Babin]

You should use the ground pin of the regulator if they're all L7xxx types.

 

[mike49504]

regulator seem to be working fine

 

[Perry Babin]

The word 'seem' is not definitive. Did you check every regulator and the output voltage was the rated voltage (±5%)?

 

[mike49504]

Ok found 2 of them measuring way off..

7912

Black probe on first leg red probe on leg 3 i get -29.84 volts on 2 of them

 

[Perry Babin]

I would expect at least one 7812 or 7815 to be out also.

 

[mike49504]

Well i talked to my friend and asked him what regulators came out of the amp to begin with.. Since theese are changed out..

He wasent 100% sure but he says he's 75% sure that the 7812's were in this amp .. Well right now 7912's are in thoose locations and thats how i got the amp in for repair..


The Board locations are U4 U5 Is there anyway to tell if the 7812's or 7912's are suppose to be in thoose locations??

 

[Perry Babin]

The negative terminal of the output filter cap for the regulator will be on the center leg of a 781x regulator. If it's a 791x regulator, the negative terminal of the output filter capacitor would be connected to leg 3 of the regulator.

 

[mike49504]

SO your talking the cap that connects to the output filter inductors??

 

[Perry Babin]

No. The output filter capacitor for the regulator. Virtually all regulators have capacitors connected between their output terminals and ground.

 

[mike49504]

Ok there are 2 radial caps that connect to the middle leg of the regulators..

The caps are a 0.1 mf i believe (104) so the regulators should be the 7812's
correct??

 

[mike49504]

Ok if i put the 7812's in the amp goes straight into protection mode...

there are 4 220 uf 25 volt caps that sit right in front of the reegulators..

The 3rd leg connects to 2 of the caps positive terminal..

The center leg of the regulator connects to all 4 caps negative terminal..

So which regulator would be correct??

 

[Perry Babin]

78

 

[mike49504]

Ok so if i put the 7812's in the amp goes straight into protection mode...

Any ideas on where to check to see why its going into protection?

 

[Perry Babin]

I don't have any information on this amp and have never worked on one so beyond telling you to check the various power supply voltages, there's not much I can help with.

 

[mike49504]

Ok Thanks for the help so far i will try trouble shooting this amp somemore and see what i can come up with

 

[Perry Babin]

dB-r.