Need Help with Linear Power 3.2HV

[Itsme]

hello, i have a Linear Power amp that isn't working. I am pretty sure the power supply is working, but no output.
Any advice would be greatly appreciatted.

 

[Perry Babin]

You need to confirm that the power supply is working. Measure the voltage on the output transistors. With your meter set to DC volts and the amp powered up, measure the voltage from the case of an MJ15022 to the case of an MJ15023. If you get no voltage, go to the mounting screws for the transistors.

How much voltage is there across the transistors?

 

[Itsme]

You need to confirm that the power supply is working. Measure the voltage on the output transistors. With your meter set to DC volts and the amp powered up, measure the voltage from the case of an MJ15022 to the case of an MJ15023. If you get no voltage, go to the mounting screws for the transistors.

How much voltage is there across the transistors?

I'm not getting any voltage from the 022 to the 023's and nothing from them to the m screws of the 2n5302's. But I do get 12.8 volts from B- to 2n5302 cases. Hope that helps?

 

[Perry Babin]

If the power supply IC is an SG3526, is there ~12v on pin 17?

Look up the datasheet if you don't know how the pins are numbered.
http://www.onsemi.com/pub_link/Collateral/SG3526-D.PDF

 

[Itsme]

If the power supply IC is an SG3526, is there ~12v on pin 17?

Look up the datasheet if you don't know how the pins are numbered.
http://www.onsemi.com/pub_link/Collateral/SG3526-D.PDF

No voltage from B- to pin 17

 

[Perry Babin]

Measure the DC voltage on pins 1, 2, 3 and 8 of the 555 timer IC.

http://www.national.com/images/pf/LM555/00785103.pdf

 

[Itsme]

Measure the DC voltage on pins 1, 2, 3 and 8 of the 555 timer IC.

http://www.national.com/images/pf/LM555/00785103.pdf

I think mine is a MC1455P1
http://www.onsemi.com/pub_link/Collateral/MC1455-D.PDF

Anyway i measured it.
1.) 0
2.) 12.43
3.) 11.69
8.) 12.37

 

[Perry Babin]

Pin 3 should be near ground. When you apply remote voltage, does the voltage on pin 6 begin to rise slowly?

Post the voltage for the rest of the pins on the 555.

 

[Itsme]

Pin 3 should be near ground. When you apply remote voltage, does the voltage on pin 6 begin to rise slowly?

Post the voltage for the rest of the pins on the 555.

I don't see a 555 timer on the board. i have been measuring from a MC1455P1 timer. I hope this is right??? Anyway pin 6 with no power is 0.60 and then goes to 0 (grounds) No voltage when amp is on.

1.) 0
2.) 12.43
3.)11.72
4.) 12.35
5.) 1.30
6.) 0
7.) 0
8.) 12.36

http://www.onsemi.com/pub_link/Collateral/MC1455-D.PDF

Here is the data sheet for the MC1455P1......

 

[Perry Babin]

That IC is the same as the 555.

When you apply remote voltage, does the voltage on pin 6 slowly rise to ~2/3 of the voltage on pin 8 then drop back to 0v?

If not, there may be a defective capacitor between pin 6 and ground.

 

[Itsme]

That IC is the same as the 555.

When you apply remote voltage, does the voltage on pin 6 slowly rise to ~2/3 of the voltage on pin 8 then drop back to 0v?

If not, there may be a defective capacitor between pin 6 and ground.

No, It just immediatly goes to 0.

Where would I look for the capacitor?

 

[Perry Babin]

It should be very near the 555. It's likely to be a small electrolytic. One leg will be connected to pin 6. The other will be connected to ground.

If it's defective and you remove it, the amp should come on but without the normal delay.

 

[Itsme]

On the bottom of the board pins 6 and 7 are soldered together and the go to a resisitor and then a capacitor.
Pin 5 goes to a resistor that is soldered to the turn on remote wire.

 

[Itsme]

It should be very near the 555. It's likely to be a small electrolytic. One leg will be connected to pin 6. The other will be connected to ground.

If it's defective and you remove it, the amp should come on but without the normal delay.

Should the pins 6 and 7 be soldered together? and pin 5 go to the remote turn on wire?

 

[Perry Babin]

I could be mistaken but there should be a small electrolytic (~1-10uf) connected directly to 6 and 7.

6 and 7 should be tied together. Pin 5 may go to a resistor then to the remote but not directly to the remote.

 

[Itsme]

I could be mistaken but there should be a small electrolytic (~1-10uf) connected directly to 6 and 7.

6 and 7 should be tied together. Pin 5 may go to a resistor then to the remote but not directly to the remote.

I followed 6 and 7 to a 25v 220uf cap. I am going to replace it real quick and see if that was it.

 

[Itsme]

The closest I have is a 16v 220uf. Do you think it would be strong enough?

 

[Perry Babin]

Yes.

 

[Itsme]

Didn't work. sorry

 

[Itsme]

There is a 1500k ohm resistor between remote lead and number 5 pin that I can not get to read on my meter no matter what it is set to. Do you think this may be it???