[TechAssist] Re: Toshiba VCR, M-725C, power supply blown
- From: "Jeff Dougherty" <jeff@xxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 16 Mar 2002 00:31:09 -0500
Gary,
Check Q**2, off the chopper, possibly leaky. Use your ohmmeter to check.
Jeff
FAX 717-564-4952
Jeff Dougherty
Intrepid Video & Electronics
501 Luther Rd
Harrisburg, PA 17111
717-909-8844
VCR tips, electronics info & general interest.
www.intrepid-video.com www.tech-repair.net www.thetoolcaddy.com
----- Original Message -----
From: "Gary McCartney" <number63@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, March 15, 2002 4:07 PM
Subject: [TechAssist] Toshiba VCR, M-725C, power supply blown
>
> This VCR came in with a minor problem and now the power supply is
> killed.
>
> Problem was that during play, if FF was pressed, then PLAY pressed
> again, the picture would switch between clean video and video full of
> severe lines (such as tracking off), about every two seconds. This did
> not occur when VCR was cold.
>
> I found that if I applied freeze spray to D831 in power supply, that
> this symptom would clear up. With no schematic, I decided to replace
> this little glass diode with an ECG552, figuring it was a B+ rectifier,
> fast switching. Plugged unit in and it was completely dead, no display
> and no functions at all. Unplugged and check circuit board for solder
> splashes and shorted parts, found none. Put original diode back in and
> still dead. While measuring PS voltages, fuse blew and chopper
> transistor has very hot and shorted. I managed to get voltages off
> chopper first. C= 165V, B= 0.43V, E= 0V. Also found 0V on cathode of
> D822 B+ rectifier in secondary. I have since checked transistors, caps,
> etc. in PS. and I don't find anything wrong.
>
> Just wondering if D831 is supposed to be a zener? The symbol on the pcb
> is that of a regular diode. numbers on the diode are: A 3 3
>
> Does anyone have a schematic of the power supply?
> --
>
>
>
> Gary McCartney
>
> McCartney Electronics
> 7134 Fife Rd, RR 7
> Guelph Ontario Canada N1H 6J4
> Fax: (519)821-1530
> email: number63@xxxxxxxxxxxxx
> ------------------------------------------
> Make your TechAssist database better!
> Submit Repair Tips here: http://www.tech-assist.org/secure/tip/
> ------------------------------------------
> To UNSUBSCRIBE your email address, click here:
> mailto:techassist-request@xxxxxxxxxxxxx?subject=unsubscribe
> Or send a BLANK email with unsubscribe in the
> SUBJECT field to the address above.
>
------------------------------------------
Make your TechAssist database better!
Submit Repair Tips here: http://www.tech-assist.org/secure/tip/
------------------------------------------
To UNSUBSCRIBE your email address, click here:
mailto:techassist-request@xxxxxxxxxxxxx?subject=unsubscribe
Or send a BLANK email with unsubscribe in the
SUBJECT field to the address above.
Other related posts:
