VQC20/50B-M2- Base unit Cap Blew- replaced now not getting correct monitor voltage

sophtayl · Feb 1, 2020

Hi guys,

looking for some knowledge.

One of the big blue Caps let go the other day (3200 uF) so I replaced both of them with 2 new units (3300uF). Everything meters out ok except for the Ch42 Converter monitor voltage. I have 295V at the Caps/ Diode stack and into the SEI01 board. This should translate to 7.4V-7.5V at ch42 (to match CH43) but I've got 6.2V with the trim pot all the way up.

I'm not sure why the Cap let go, possibly age but may be this also has something to do with it?

Has anyone experienced a similar issue? Any suggestions on where to go next to test the monitor circuit and how the 295V gets conditioned?

thanks

Mick

doug8cat · Feb 1, 2020

Can you supply me with a schematic? No promises but I think I can help.
Just PM me and I will give you my contact info.

cnctoolcat · Feb 1, 2020

Have you found the service manual online for the FR-SE yet?

The DK hybrids can go bad (and related diodes, resistors, etc.), base transistor(s)...

You need accurate voltages from the power supply pins into the SE-IO1. Make sure all are making good contact.

Replace all capacitors, if it hasn't been done....it's cheap to do.

ToolCat

sophtayl · Feb 1, 2020

doug8cat said:
Can you supply me with a schematic? No promises but I think I can help.
Just PM me and I will give you my contact info.

Unfortunately no schematic for it as the issue is the conditioning on the sei01 board and I have not been able to source a schematic for it

Sent from my SM-G930F using Tapatalk

sophtayl · Feb 1, 2020

cnctoolcat said:
Have you found the service manual online for the FR-SE yet?

The DK hybrids can go bad (and related diodes, resistors, etc.), base transistor(s)...

You need accurate voltages from the power supply pins into the SE-IO1. Make sure all are making good contact.

Replace all capacitors, if it hasn't been done....it's cheap to do.

ToolCat

Yes these all tested ok. I also have spare new replacements for the dks but the wave forms are good. Caps were all changed 12 months ago also

Sent from my SM-G930F using Tapatalk

sophtayl · Feb 2, 2020

Quick update.
I managed to get the machine going by fixing my old sei01 board. (Been on the to do list but needed to chase a couple of shottky diodes and transistors that I borrowed from faulty board.) Will have a further interrogation of the faulty board once I replace some components I had to borrow.

Sent from my SM-G930F using Tapatalk

Search

Largest Manufacturing Technology Community on the Web

Search

VQC20/50B-M2- Base unit Cap Blew- replaced now not getting correct monitor voltage

sophtayl

Cast Iron

doug8cat

Titanium

cnctoolcat

Diamond

sophtayl

Cast Iron

sophtayl

Cast Iron

sophtayl

Cast Iron