I just got a dead Zenith VR9775PT Beta deck with orignal remote and instructions - Videokarma.org TV - Video

Electronic M · #1 08-10-2011, 01:10 PM

It is in good cosmetic condition, but will not power up in anyway. The only reason I don't suspect the power cord is that the power outlet on the decks back works. The deck is very clean inside and power supply board looks like new. I don't have a schematic for it. I've never done electronic repair on VCRs before, and am more of a tube radio and TV hobbyist so I have no idea where to start. Please help me get this fixed.

Some kind soul put a slip of paper in the folded up cord with the sam's folder #(VCR-73) so it is clear that someone other than me wanted to see this unit fixed up.

Tom C.

ChrisW6ATV · #2 08-10-2011, 02:08 PM

Zenith Beta VCRs were all clones of Sony models. That one looks like a clone of the Sony SL-2500, which was the first low-profile, stereo-component-style VCR that I remember. Here are some pictures:

http://www.betamaxcollectors.com/son...elsl-2500.html

The power supply on this should not be too complex, so basic troubleshooting techniques should get you started, even without that Sams manual. (Trace from the power cord and switch to see if it uses a power transformer first, and if it does not, plug it into an isolation transformer to do your repairs. Check voltages from the transformer output, then from the whole power supply which may have its terminals marked where they connect to other boards, and so on. Do visual checks on electrolytic capacitors, but ideally use an ESR meter on each one in the PS, as a start.)

Jeffhs · #3 08-10-2011, 02:30 PM

Once you do get this deck running, I wonder how you'll test it, since Beta videocassettes are difficult (if not downright impossible) to find nowadays.

Electronic M · #4 08-10-2011, 02:32 PM

Okay I'll open her up later today and see what I can find.
I do have a working capacitor which is from the 50's (Heathkit C-3) the lowest leakage test voltage setting it has is 50V so I may not be able to use it. I did reciently get some other tube era cap checkers that have more features that I may fix and use if they will work with something this new.

Before I posted this topic I did a visual examination of the top of the PS board, and it looked new. No dust, bulging caps, or overheated looking parts could be seen. I beieve there were some small power transformers on the board.

Guess it is time to whipout the DMM and C-3 and start troubleshooting.

Tom C.

Electronic M · #5 08-10-2011, 02:41 PM

I have 7 tapes and 5 beta decks(two work, two semi-work, and then there is my new dead one).
Two of those tapes are the Hi Fi Beta Gone With the Wind box set, one is a unopened souviner tape of the Statue of Libertys centennial, and the rest are all home recordings.

My working betas are a plane jane sanyo and a Hi Fi Toshiba.
My semi-functional units are a non-Hi Fi Sony superbeta, and the first Zenith brand toploader.

Tom C.

Electronic M · #6 08-10-2011, 09:03 PM

update part of the power supply works! By shorting the terminals on a relay on the ps board I was able to get most of the deck to come alive! The main clock, channel, etc display refused to work along with remote and manual power buttons.
It did play one of my tapes quite splendidly!

Also the "video action" switch on the deck worked well, but the remote would not change it's mode. All other functions of the remote seemed to work well. It does not use a power transformer connected to the power cord, but instead bridge rectifies the line and feeds it in to other circuits that I get lost trying to trace.

I think it is time to bite the bullet and cough up the exhorbitatant 22$ for the sam's off their site.

I'm happier now that I know that it mostly works (which gives me the motivation to push foreward).

Tom C.

Electronic M · #7 08-11-2011, 10:22 PM

Well I'm confused I replaced most of the power supply caps though some of the replacements from radio shack did not test much better than the originals.

I'm getting reasonable voltages from the ps with the relay shorted, but the display refuses to work despite having voltages in the 20-30V range on it. what is more the only way to coax any life out of the electronics is to short the PS relay.

My folks voted to defund my bit of schematic pork so I'm still flying blind on this deck and have no idea if the voltages I'm measureing are right or not.

If anyone has a copy of the manual and can give me info on the ps circuit it would be appreciated.

Tom C.
BTW my last post was wrong. There is a transformer directly connected to the power line. I just missed it last time.

mstaton · #8 08-12-2011, 12:26 AM

Hopefully that fluorescent display is good. They get dimmer and dimmer over time and then fail completely. Hopefully this is not the case. More than likely it's a power problem

Electronic M · #9 08-12-2011, 03:59 PM

Well the display is not burnned out it just won't light on its own. I'm able to light it by touching the chassis with one finger and running annother finger over the terminals, or at least I was untill a moment ago.

This thing is confusing as all heck with out a schematic.

I'm worried that my pokeing arround is gonna do more harm than good so I may button it up and squirrel it away untill I get a schematic.

Tom C.

Electronic M · #10 08-12-2011, 05:53 PM

I did not button it up quick enough. On the last forced powerup it loaded on its own with no tape then locked in fast foreward. I think one or more of the control chips may be fried.

I'm not sure what to do with it now. Maybe I should sell it.

Tom C.

ChrisW6ATV · #11 08-13-2011, 08:14 PM

A couple of notes:

-Since the display is powered at all times but the relay-controlled circuits are not, you probably have problems in the always-on power supply but not the relay-controlled one, if this is possible.

-20-30V seems very low for that fluorescent display, probably why it is not working. That also means you could "zap" yourself if you touch its terminals randomly too much and you DO find a spot with the correct voltage.

-Your Heathkit capacitor tester is for measuring capacitance and perhaps leakage (both important in high-voltage, low-capacitance parts), but it probably does not measure ESR, which is more important than actual value in electrolytic caps. If you intend to work on more solid-state equipment long term, an ESR meter would be a great investment, or you could also build one; it is essentially an audio oscillator that couples its signal through the cap and measures the output.

-I am glad you found a transformer in there after all; tinkering with hot-chassis (transformerless) stuff is dangerous without an isolation transformer (and could be lethal with actions like "terminal-touching"!).

-Did you find any markings in the power supply of voltages on any of its connections to other boards? Sony items often have them (and this is a rebadged Sony VCR).

Electronic M · #12 08-13-2011, 08:50 PM

I did not notice any voltage markings on it though most of the voltages from the supply made sense. There were a few 12.6V sources, a 5.1V, and a 9.something.
I don't think my folks will spring for the Sam's for a while, so I will probably end up working on my first gen Zenith topload beta before this one as I actually have the Sam's for the older one.

Electronic M · #13 08-13-2011, 08:57 PM

Ohh, and I almost forgot I believe my Heathkit has some type of esr capability. I was informed in a thread I posted on it that the degree one has to rotate the power factor knob to fully open the the eye correspondes to the ammount of ESR.