HR2510 Driver Bias problem.

[Low_Boy]

This was a non working parts radio when I got it. It is now working but I am having a driver bias problem. It started out with a bad bias diode it swung my meter all the way over infact slammed it all the way over. I installed another MV1yH diode. Now I can only get about 8mA bias. it should be 50mA.
VR113 is good.
driver is good
final is good and new.
R158, R161 and R162 all good.
No glue on L124 and L134 and all parts in that area.
I did notice checking against a working radio. The single leg of VR113 where it gets it power on the radio where the bias can not be set VS. a working radio is .010 bad radio VS .001V on a working radio.
What parts am I missing? or any thoughts appreciated.

 

[sp5it]

Use for bias 1n4148 or any other silicon diode for a test.

 

[Low_Boy]

Use for bias 1n4148 or any other silicon diode for a test.

Tried it. Now getting 13mA. A little improvement.

 

[sp5it]

So if bias diode is OK and there are changes when you turn bias VR I think driver is defective.

 

[Low_Boy]

MV1YH is two diodes. For testing will only one work?

 

[sp5it]

Sure it will. I usually replace them with 4148 and work forever

 

[Low_Boy]

I will then try another driver. The one in the radio tested good but hoping that is the problem.
Thanks Mike

 

[Low_Boy]

Bad driver and I believe it is a fake 2SC2166.my DCA55 meter never let me down the driver tested good with a HFE 44. The new Mitsu. 2SC2166 had a HFE 31. I never saw a real
2166 with the 2 indents at the top and the flange looks different.
I should have known.
Thanks Mike
Just noticed the flange is shinny. Never saw a real one with a shanny mounting flange.
Edit,,, I am wrong. Took a closer look at a real 2SC2166 and they have the dots. I am totally baffled.

 

[Handy Andy]

Don't be...it happens.

Many fakes are rebadged other parts that can fool some testers.

You're not the only one that has found this out - I've seen "Barrier Diodes" used in Automotive wiring to help with directional indicators and even DRLS - pass a tester as a Good Transistor - with "Odd but close" Hfe ratings.

​

That's the Clue - look on the Datasheet - or remember the Hfe number from it, - then you'd know that the parts are TOO good to be true.

IF the Hfe rating is not in the typical range - but either too close to LOW or too High - More to the "low side" - then you have the Questionable part...(Failed Transistor)

 

[Low_Boy]

Thanks Andy. First instinct was replace driver. Then it tested good. I then started testing parts in the radio and found nothing was bad. Live and learn.

 

[nomadradio]

MV1YH is two diodes

One diode. MV13Y has two.

Good job on this one. Fake parts have become a scourge.

73

 

[Low_Boy]

One diode. MV13Y has two.

Good job on this one. Fake parts have become a scourge.

73

OOps. Thanks nomad.