Toshiba W-603 VCR problem

Check for high ESR caps in the power supply. You will need an ESR meter to do so.

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JANA _____

The SMPS seems to be at the correct voltages printed on the PCB. I got the carriage to lower as if a tape was being inserted. Sometimes the display works, sometimes not. The VFD filament voltage is present. The loading motor and reel motor just moves in little bursts every 0.5 second or so, then occasionally both run for about 1 second straight. Then it goes back to short bursts. If I unplug it, it continues with the erratic motor motion. The entire display will sometimes blink along with the motor motion.

However, there is a 5.8V supply that drops by about 1 volt (very short drop, a few milliseconds) every time the motors move. The odd thing is, this periodic voltage sag still occurs even when the VCR appears to be completely dead.

This VCR was working one hour, then quit working. No electrical storms or anything unusual. Only I had access to it. I'm familiar with electronics, but not a VCR expert. Any suggestions?

I found the problem. I had a feeling it was power supply caps too. But it wasn't one of the output filter caps, it was a 22uF non-polarized cap on the primary side of the switching xformer. It measures 0.1uF with my LC53 Z meter.

Sucks it's a non-polar; out of the hundreds of caps in my stock, I have none of these type.

These were Samsung - built and they also made lots of models for RCA, (RCA VR506, Samsung VR3701, etc).

There's an RCA part number for this cap - it's fairly cheap, if it's available that is.

I'll try to look it up and repost.

Also, one could probably get it from bdent.com

Mark Z.

snipped-for-privacy@yahoo.com wrote:

RCA number 194339. There's normally 2 caps in there, just pitch the smaller one or throw it in the old parts drawer...

Mark Z.

Use two 47 uF connected in series back to back ( positives shorted, negatives soldered in circuit)?.

BTW 22uF isn't critical, these units work up until the cap is almost open. I'm sure a 10uF would work fine.

mz

I'm not going to bother getting the "exact replacement"; I'm just going to get a generic non-polarized cap. But what I'm wondering is, how robust is hooking two regular electrolytics together, + to + to make a non-polar cap?

snipped-for-privacy@yahoo.com wrote in news: snipped-for-privacy@11g2000cwr.googlegroups.com:

Fairly robust PROVIDED you use diodes [properly rated to handle the currents and voltages] across each cap to prevent back biasing it during the other cycle.