pvision

Tantalum cap values for Dynacord VRS-23
« on: January 06, 2021, 07:39:03 AM »
I have a Dynacord VRS-23 on the bench that is pulling the +ve voltage rail down to near-zero when powered up. The main board is littered with tantalums and with 22 uF decoupling caps

The documentation I've found doesn't give values for the tantalums. Has anyone experience with replacing these and have a list of values?

Also the red el caps (Frakos?) seem to be in two types - some (most 22/40) have polarity markings and some (mainly 22/16s) don't. What do I infer from this?

Thanks for any help!


Re: Tantalum cap values for Dynacord VRS-23
« Reply #1 on: January 06, 2021, 08:52:41 AM »
Hello

I have a Dynacord VRS-23 on the bench that is pulling the +ve voltage rail down to near-zero when powered up. The main board is littered with tantalums and with 22 uF decoupling caps

The documentation I've found doesn't give values for the tantalums. Has anyone experience with replacing these and have a list of values?

Also the red el caps (Frakos?) seem to be in two types - some (most 22/40) have polarity markings and some (mainly 22/16s) don't. What do I infer from this?

Thanks for any help!

I found this
http://www.florian-anwander.de/dynacord_vrs23/
Service manual have pcb layout and schemo.

Tantal look like 10u according to quick check at the service manual
Alu without polarity are bipolar.
For what I find looking at some pictures around, Roederstein EKU series (the other with + mark on top are EK)

Best
Zam

Re: Tantalum cap values for Dynacord VRS-23 New
« Reply #2 on: January 06, 2021, 10:36:58 AM »
I repaired two of these great delays years ago. Both had exactly the problems you describe. It was always defective tantalum capacitors, whereby the red Roedersteins Frakos also like to die early.

Sometimes the voltage regulator dies with the capacitor that caused it. If I remember correctly, I had to replace it once.
« Last Edit: January 06, 2021, 03:23:14 PM by rock soderstrom »

pvision

Re: Tantalum cap values for Dynacord VRS-23 New
« Reply #3 on: January 06, 2021, 12:45:42 PM »
Thanks. I started with the voltage regulator. Next I'll replace the diode across it - I learnt that from a dbx 160XT

After that I think the shotgun approach to the tants is in order. I can confirm they are 10/35

Thanks for the help with the red caps: they are 22/40 and 22/16 bipolar
« Last Edit: January 06, 2021, 01:47:44 PM by pvision »


 

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