Atomic AT-5000.1D

[S Merlington]

I got this amp in for repair ..

For the regulators someone wrote on the board 7815 next to U9's location But there is a 7812 in the location right now..


How do i tell if a 7815 or a 7812 goes in U9's location ??

 

[timwebb]

7812should be pos 12v. 7815 should be pos 15v.

 

[S Merlington]

Yeah but i need to know which one is the right 1 for U9's location

 

[timwebb]

it should have 12 or 15 volts on each one.

 

[Perry Babin]

7815 if the output goes to the first pin of the center group of pins on the driver board.

 

[S Merlington]

Ok I figured the regulator problem out..

Got the power supply up and running...


The Audio Driverboard and Outputs Are NOT Installed yet...

I get 0.12 volts on the output filter inductors

On the D1302's Black probe on leg 1 Red probe on Leg 3 i get 0.48 volts


I checked the Protection circuit And Q1 (A1266) tests fine all other components in that circuit also test good..


Any ideas on what to check next since im getting DC on the output filter inductors and the D1302's are being driven on with no Audiodriverboard or outputs installed yet ??

 

[Perry Babin]

0.12 is insignificant. Did you have the black probe on the secondary ground?

 

[S Merlington]

Yes black probe was on center tap

So as far as the D1302's being driven on Would that problem likely be in the Protection circuit ?

 

[Perry Babin]

I'm not sure what the threshold voltage is for the 1302s. I'm not sure that it would be 'on' at 0.48v.

 

[S Merlington]

Well both transformers have problems with them..

If i twist them i can watch the voltage on the 1302's go up to 5 volts if i twist them the other way i can get the voltage to drop to 0.01 volts..


When i was twisting them i blew 1 power supply fet and i removed it now the amp is stuck in protection mode..

 

[Perry Babin]

The problems are generally where the terminal windings meet the rest of the windings.

If you can't find it, disconnect the amp completely and connect the B+ through a current limiter. Connect the 12v power supply ground to the secondary ground. Twist the transformer. Does the current increase when you twist the transformer?

Does it arc when you twist and release (or twist the other way) as the current increases/drops to 0?

 

[S Merlington]

I saw one of them arcing fixed that but both of the transformers will increase and decrease the voltage on he D1302's the amp will start drawing excessive current ...


If i touch either transformer i get zapped everytime..

 

[Perry Babin]

It may be OK if there isn't a direct short.

You get zapped because the enamel doesn't have sufficient dielectric strength and the voltage is leaking through. This is a problem on a lot of the larger amps.

 

[S Merlington]

Now i have to find out why 1 time the amp will stay in protection and then if i wait for awhile and power it back up it will come out of protection and draw 20 amps of current..

Power supply fets will heat up as well..

 

[Perry Babin]

If the output transistors are not being driven off quickly enough, it could be going into protect and if the threshold level for the over-current protection is just at the level of current it's drawing (due to the outputs not being driven properly), it could be simply drawing current (but not quite enough to trigger the protection circuit).

Do the outputs get hot when it's drawing 20 amps?

 

[S Merlington]

The outputs The audio driverboard and the Rectifiers are all out of the amp at the moment trying to figure out why the amp will be in protection 1 time then the next time it will power up and draw 20 amps of current

 

[Perry Babin]

Are you sure that you don't another intermittent short on the transformers?

 

[S Merlington]

Im checking that right now

 

[S Merlington]

Ok Power supply is up and running in this amp..

I installed the Audio Driverboard..

Outputs are still out of the amp..

Heres what i get on the Pins for the Audio Driverboard Do thees voltages look correct??

Pin 1:-156.0
Pin 2:-144.9
Pin 3:-157.2
Pin 4:1.60
Pin 5:1.60
Pin 6:-157.4
Pin 7:1.60
Pin 8:1.60
Pin 9:-157.4
Pin 10:-157.4
Pin 11:-157.4
Pin 12:1.18
Pin 13:16.49
Pin 14:6.58
Pin 15:1.61
Pin 16:1.60
Pin 17:-3.24
Pin 18:1.62
Pin 19:-157.4
Pin 20:-157.4
Pin 21:-145.2
Pin 22:-157.4
Pin 23:1.60
Pin 24:1.60
Pin 25:-157.4
Pin 26:1.60
Pin 27:1.60
Pin 28:-157.4
Pin 29:-157.4

 

[S Merlington]

See post above..

I installed the outputs and powerd the amp up it ideas perfectly but i get no output..

Heres what i have on the D1302's with black probe on leg 1..

D1302

Leg 2:0.00
Leg 3:0.60

D1302

Leg 2:0.00
Leg 3:0.60