Just picked up a Panasonic PV-1730 Hi-Fi VCR

[vortalexfan]

Originally Posted by Ed in Tx

Be sure to check for a shorted electrolytic capacitor somewhere in that motor drive circuit too, could be something as simple as that. As old as it is that's a possibility.

Well I looked through the service data and I found 4 electrolytics in particular that seem suspect in the motor drive circuit that could be causing my issue, C18 (C1118 in the Sam's), C30, C32, and C34 (C2530, C2532, and C2534 respectively in the Sam's) that are all in the 11.9V Source (15V) rail, and the 12V Source rails for the supply and take up reel motors.

One in particular looked kind of out of place (it looked a little newer than the rest of the capacitors in the unit and also it was a higher capacitance rating than what's called out in the Sam's), which is C30 (C2530) which is supposed to be a 100 µF 16V but instead had a 470 µF 16V capacitor in that spot, which unless there was some sort of design change made to the unit that wasn't reflected in the Sam's (or that was reflected in the Sam's) I think someone installed the wrong size capacitor in there, which I'm apted to think that someone put the wrong size capacitor in there because as I said the capacitor was a completely different style of capacitor than the rest of the capacitors in there.

[Ed in Tx]

Originally Posted by vortalexfan

Well I looked through the service data and I found 4 electrolytics in particular that seem suspect in the motor drive circuit that could be causing my issue, C18 (C1118 in the Sam's), C30, C32, and C34 (C2530, C2532, and C2534 respectively in the Sam's) that are all in the 11.9V Source (15V) rail, and the 12V Source rails for the supply and take up reel motors.

One in particular looked kind of out of place (it looked a little newer than the rest of the capacitors in the unit and also it was a higher capacitance rating than what's called out in the Sam's), which is C30 (C2530) which is supposed to be a 100 µF 16V but instead had a 470 µF 16V capacitor in that spot, which unless there was some sort of design change made to the unit that wasn't reflected in the Sam's (or that was reflected in the Sam's) I think someone installed the wrong size capacitor in there, which I'm apted to think that someone put the wrong size capacitor in there because as I said the capacitor was a completely different style of capacitor than the rest of the capacitors in there.

Re-read your post. It's probably OK depending where it is in the circuitry. I wouldn't necessarily trust Sam's as gospel either! Might have been a change during production.

If I had that machine first thing I would be doing is checking every electrolytic in it with my ESR meter. I actually have two, one I used at the shop and the other for home use, it's that important and useful.

[Ed in Tx]

Won't let be attach two files! What the ...??!

OK I see what's going on. I already attached that one in another thread a while back.

Another pic (right side) testing the Hi-fi audio board from an old JVC VCR. Those old surface mount caps were notorious for failing.

[vortalexfan]

Originally Posted by Ed in Tx

Re-read your post. It's probably OK depending where it is in the circuitry. I wouldn't necessarily trust Sam's as gospel either! Might have been a change during production.

If I had that machine first thing I would be doing is checking every electrolytic in it with my ESR meter. I actually have two, one I used at the shop and the other for home use, it's that important and useful.

Unfortunately my ESR Meter died recently (the LCD Display won't come on anymore) and it was one of those "kit" units that you could get on ebay for $10 (the one that could come either cased or uncased.)

The Sam's for this VCR is from 1987 and my VCR is from 1984...

[Ed in Tx]

Originally Posted by vortalexfan

Unfortunately my ESR Meter died recently (the LCD Display won't come on anymore)...

You need to get another one then. I wouldn't even attempt to fix this old stuff without an ESR tester. Can save hours of work, and the old equipment you're trying to fix.

[vortalexfan]

Originally Posted by Ed in Tx

You need to get another one then. I wouldn't even attempt to fix this old stuff without an ESR tester. Can save hours of work, and the old equipment you're trying to fix.

I just did, I bought an old analog one.

I have posted a screenshot of the section of the schematic with the capacitors in question including the 470 uF 16V Capacitor and its overall circuit context.

[Ed in Tx]

Originally Posted by vortalexfan

I just did, I bought an old analog one.

First ESR meter I ever used was an analog one, Capacitor Wizard I think it was called. The shop owner bought it in the mid-80s for us technicians to share. I got tired of having to track it down every time I wanted to use it and found the black digital one, a kit from Dick Smith Electronics in Australia, so I could have my own. Still works great!

[vortalexfan]

Originally Posted by Ed in Tx

First ESR meter I ever used was an analog one, Capacitor Wizard I think it was called. The shop owner bought it in the mid-80s for us technicians to share. I got tired of having to track it down every time I wanted to use it and found the black digital one, a kit from Dick Smith Electronics in Australia, so I could have my own. Still works great!

I saw some capacitor wizards for sale on epay but the price was too rich for me, $275!

I ended up getting a MAT Electronics Analog ESR Meter model MUL3333 that can test capacitors in-circuit and it was only $45 (I will have to use the cables from my old ESR Meter as the original cables didn't come with this unit but they were basically just your standard mini-banana plug style cables.

so what do you think of the circuit diagram I uploaded showing the capacitors in question?

[Ed in Tx]

Originally Posted by vortalexfan

I saw some capacitor wizards for sale on epay but the price was too rich for me, $275!

Yikes! They were expensive back then too but not that much!

I ended up getting a MAT Electronics Analog ESR Meter model MUL3333 that can test capacitors in-circuit and it was only $45 (I will have to use the cables from my old ESR Meter as the original cables didn't come with this unit but they were basically just your standard mini-banana plug style cables.

Sounds like a deal. Both of mine test in-circuit. As long as the applied AC voltage is below the conduction point of the semiconductors in the circuit .6 V or less they will do that no problem.

so what do you think of the circuit diagram I uploaded showing the capacitors in question?

I'll look at it in a little while. Busy fixin' food.

[vortalexfan]

Originally Posted by Ed in Tx

Yikes! They were expensive back then too but not that much!

Sounds like a deal. Both of mine test in-circuit. As long as the applied AC voltage is below the conduction point of the semiconductors in the circuit .6 V or less they will do that no problem.

I'll look at it in a little while. Busy fixin' food.

Ok, thanks! And that's good to know.

[Ed in Tx]

Originally Posted by vortalexfan

so what do you think of the circuit diagram I uploaded showing the capacitors in question?

That's no problem being larger value, it's on the 12V B+. Might have been a production change to fix some ripple or interference when the motors were loaded down. In that diagram they show 2 100 uF's in parallel for total 200 uF.

[vortalexfan]

Originally Posted by Ed in Tx

That's no problem being larger value, it's on the 12V B+. Might have been a production change to fix some ripple or interference when the motors were loaded down. In that diagram they show 2 100 uF's in parallel for total 200 uF.

Ok, I wasn't sure, I knew in old tube equipment, capacitor values weren't too critical but I wasn't sure about solid state stuff ( I know some solid state stuff like this capacitor value is more critical, than in tube circuits, which is why I asked.)

[Ed in Tx]

Originally Posted by vortalexfan

Ok, I wasn't sure, I knew in old tube equipment, capacitor values weren't too critical but I wasn't sure about solid state stuff ( I know some solid state stuff like this capacitor value is more critical, than in tube circuits, which is why I asked.)

And I would think tube equipment would be more critical than solid-state...

[old_tv_nut]

How critical a capacitor value is depends on its function, and has relatively little to do with tube vs. solid state. Power supply filter caps need to be a certain minimum size. Signal-handling cap tolerance depends on function. Stage-coupling caps need medium-tight tolerances to assure low-frequency response. Caps for functions like tuned circuits require the tightest tolerance.

Tube and transistor circuits are similar in their sensitivity to passive component values.

Tube amplifiers generally may be sensitive to individual tube parameters, while most transistor circuits are generally insensitive to transistor parameters above a certain minimum, for example if current gain (beta) >=100. There are exceptions, for example where matched transistors and/or diodes are required to maintain proper bias in push-pull power stages.

[Ed in Tx]

Originally Posted by old_tv_nut

How critical a capacitor value is depends on its function, and has relatively little to do with tube vs. solid state...

Good clarification. Thanks!

I've always avoided working on anything with vacuum tubes including CRT TVs. Reason why is, back in the '70s my Aunt and Uncle up in Connecticut came home to find my cousin dead on the living room floor. He had been working on a tube-type guitar amplifier. So I've been a bit wary ever since.

Although one of these can nail 'ya too, about 80V + and - on the finals... one of my Pioneer SPEC-4 power amplifiers that decided to let the smoke out one day.