Rectifier help if possible please

[Guisey]

Hi, anyone familiar with the rectifiers on Kortek chassis? Mine is the KTN-20.

Screen went off, found fuse F601 blown. With some digging about online for info, checked the rectifier to find a short.

Replaced the rectifier with 4 1N4007 diodes (checked schematic for the direction of them)

Decided to do a full recap whilst it was on the bench, swapping every cap like for like (the electrolytic ones anyway)

Now on powering up I'm getting strange 'wobbling' at the edges of the picture.

Comments on UKVAC FB page suggest voltage issues and horizontal hold, I've had a play about with H hold with no joy. I'm guessing it could be down to my 'repair' and maybe wrong diodes. Even with the service manual I can't find a datasheet for the OG rectifier. Any help appreciated 👍

Sidenote... On initial powering up it blew my 50v 47uf cap directly next to the rectifier. I replaced with 160v 47uf. It hasn't blown but has domed a bit.

There is an isolation transformer in place.

 

[big10p]

I'm no expert, but it sounds like that cap that blew is the wrong spec. Parts lists, schems and even PCB markings don't always get it right.

What's the input voltage from the iso, out of interest?

No doubt one of the monitor experts here will be able to assist you more.

 

[gunblade]

c608? 47uf 16v
d601 i use a kbpc104 400v 3a
i reckon your regulation transistor q601 is bad, did you replace the mains smoothing cap?
b+ should be 120v

 

[Guisey]

I'm no expert, but it sounds like that cap that blew is the wrong spec. Parts lists, schems and even PCB markings don't always get it right.

What's the input voltage from the iso, out of interest?

No doubt one of the monitor experts here will be able to assist you more.

Thanks for your reply, I'll check the voltage from ISO when I can. I had thought to check it but never did.

 

[gunblade]

you need to check the regulator transistor, i think its q601 - its bolted to the frame near the fuses

 

[Guisey]

c608? 47uf 16v
d601 i use a kbpc104 400v 3a
i reckon your regulation transistor q601 is bad, did you replace the mains smoothing cap?
b+ should be 120v

Thanks for your reply, I changed every cap including filter cap. I'll check B+ voltage and also check q601. I'll grab a replacement for d601 same as you specified.

Thanks again 👍