AU-999 Restoration & Modification

[leray1]

DBT Fail. What should I check first?

 

[Hipocrates]

What should I check first?

Just outputs and rectifier replaced right?

 

[leray1]

I just checked the output transistors for continuity with the heat sink. One side is fine, the other gives me readings that fluctuate and will even be infinity in different points or positions.

 

[leray1]

Just outputs and rectifier replaced right?

No I changed out the caps, transistors and diodes on the driver boards.

 

[Hipocrates]

Remove driver boards, and test again.

 

[leray1]

With the drivers removed, a 100W bulb went bright at startup, then out. A 60W stayed out and a 53W was dim.

 

[Hipocrates]

Use the 60W.

Does the amp gave you problems before you worked the drivers boards?

 

[leray1]

Lights on unit come on but the 60W doesn't glow. There were no problems before.

 

[Hipocrates]

Re-check your drivers boards. Post some pics maybe we can catch something. If you can with good resolution.

 

[leray1]

Driver Boards

 

[Hipocrates]

Can you tell me what transistors are you using? they seem like ZTX

One thing that can happen is that the BIAS is very high too.

 

[leray1]

Yes, ZTX. How do I check the bias?

Nevermind. I found how to check bias. I'll report back shortly.

 

[leray1]

One side is near zero, the other is very high ~300mV

 

[Hipocrates]

where did you measure that?

 

[leray1]

R853 was high, R854 was low

 

[Hipocrates]

R853 was high, R854 was low

NICE! I love when people talk like that!

adjust to 14mv... just to see if pass the DBT.

 

[Hipocrates]

Now:

Acording with my notes and based in stereofun work, I have this subs

TR801 --> ZTX795A
TR803 ---> ZTX795A
TR805 ---> ZTX694B
TR807 ---> ZTX694B
TR809 Not replaced)
TR811 ---> KSC2690AYS
TR813 --->KSA1220AYS

Which ones did you use?

 

[leray1]

Adjusting VR803 does nothing to the measurement

 

[leray1]

Now:

Acording with my notes and based in stereofun work, I have this subs

TR801 --> ZTX795A
TR803 ---> ZTX795A
TR805 ---> ZTX694B
TR807 ---> ZTX694B
TR809 Not replaced)
TR811 ---> KSC2690AYS
TR813 --->KSA1220AYS

Which ones did you use?

801, 803, 805 & 807 are correct. For 811 & 813 I used ZTX795A, also.

 

[Hipocrates]

For 811 & 813 I used ZTX795A, also.

Ok ZTX795A is a PNP.

If you are using that on TR11 you will have problems, you need a NPN transistor there, maybe ZTX694B will do.