JBL-Urei 6230 Standby Fault

[Shaun M]

Hi everyone. I have a JBL 6230 Ampflier which has a fault which im trying to repair. When powering on the relay clicks and the standby light goes off but only for about three seconds. The light slowly gets brighter after these three seconds.

I got some advice when someone had a look at it, he thought it could be the caps.

I have replaced the two voltage regulators and caps C28 and C30. After this it took slightly longer for the standby light to come back on. I'm now looking at replacing the poly caps C10, C11, C15 and C14 but I feel im looking at the wrong things.

[Jorre Pulle]

Hello;

I don't know the 6230 amp,but have a lot of 6290 spares.
If you pay the shipping (from Belgium) you can get them for free.
I'd check the output transistors and driver transistors first,any DC voltage on the outputs?

Grtngs,
Jorre

[subwoof]

On the ckt board near the relay there is a electrolytic cap that goes bad with age ( HEAT ).

The engineers at urei used a 1/2 wave rectifier to create the 24v needed for the relay but it's murder on that little guy..

replace it and you will be just fine. have done hundreds over the years on many jbl/urei/crown/etc that have this design.

C32 470uf 40V

Use a 105C temp cap if you can and be sure to replace all 3 in the power supply.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-6230_%206260manual.pdf

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[Shaun M]

Hi, I replaced this cap and still have the same problem. Switch amp on, relay clicks, standby light goes off and then slowly comes back on again after a few seconds but relay doesn't click when standby light comes on.

I can't remember top of my head of the DC offset, but it was minimal.

[subwoof]

if you don't have DC on the output terminals, and the light slowly comes back on, then a cap must be involved somehow. replace the 22 and 100 caps ( C35, C13 ) on the DC detector circuit. measure the voltage across the relay coil to see how it changes.

The small transistor with the tab ( Q23 ) can be replaced with almost anything rated for 500 ma if needed.
These sometimes leak but low prob in this case. Check R42 for value too.

[Shaun M]

Many thanks for your help.

I've come across some suspect diodes CR14, CR15 and CR16. I will change these soon.

I have been thinking that it could be a leaky Q23, but will also check and or replace the caps you mentioned.

[Shaun M]

Things get even stranger now. When I measure voltage from the bridge rectifier across green and red I'm getting over 100volts DC And the voltage between the two white wires is 18volts AC!??

Surely this should be 24volts at the white wires and 52volts at the HV green and red wires?

[subwoof]

measuring across the white wires gives you the AC voltage - when rectified and filtered it becomes 24Vdc

measuring from the red to green is across BOTH sides of the rectified main DC voltage ( 50 + 50 )

[subwoof]

Have a pair of 6230's on the bench right now - one is fine, the other is in fault
( even though the amp section is just fine ).

Will let you know what I find.
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