1982 jvc hr-7300u
 

http://i.imgur.com/HuVsFHzm.jpg

http://i.imgur.com/i7mvIrBm.jpg

http://i.imgur.com/NS0ymzVm.jpg

http://i.imgur.com/rzkhvb9m.jpg

There are five belts in this unit:

http://i.imgur.com/0f6p8IBm.jpg

The square take up belt that runs from the top of the capstan to a white pulley was about 48 mm in diameter. When I replaced it with a new one of the same size, it didn't work. So, I tried smaller sizes until the take up reel turned reliably. ~40 mm did the trick.

The flat capstan belt was completely melted. It appears to have been about 101 mm in diameter. I didn't have a replacement, so I made one out of vinyl electrical tape. After six hours of testing, it still works consistently.

The loading motor belt was fine and hasn't been measured.

http://i.imgur.com/kXMHbHAm.jpg

The counter mech uses two belts. The first is ~63 mm in diameter and goes from the take up reel to a double pulley.

http://i.imgur.com/IHOpAo6m.jpg

The second belt goes from the double pulley to the counter mech. It's about 32 mm in diameter.

http://i.imgur.com/s3nDhnrm.jpg http://i.imgur.com/DRF5HpQm.jpg

There are several date code locations including: the inside of the front panel, the forward/reverse motor, and the top of the loading mech (month & day). As you can see, this unit was manufactured in December of 1982.

Unless that flat belt was wider than 1/4" I'd have made it out of rubber bands...if the band is too long or short splice it with another band and super glue.

I tried the rubber band fix which is ok and not on the capstan drive unless you want quivering sound and a shaky picture.LOL....................
One of my main apps for the rubber band trick is the capstan belt of a Toshiba beta HiFi (the original is almost exactly rubber band size) it's always ran smooth as silk with a rubber band there..... I've never known where or how to order belts so most of my mechanical equipment that did not have good belts or use ones from gear I've scrapped are 'living on office supplies' so to speak.

Looks like you can still get a belt kit from http://studiosoundelectronics.com/mbk-06.htm to restore it properly.

3 kits: Belts only, with rubber tires, and with pinch roller.

What a cool project! I've only seen one of those models back in 1999 when I put new belts on it. Hope you get it working again!

This machine isn't mine and it's mostly in storage. I don't want a rubber band dry rotting in it. Folded vinyl electrical tape wont leave a mess when the time comes.

Let me clarify:

This unit 'works' as it is. All it could use outside of a proper capstan belt is a sealed relay. The 'Omron 62V-2' relay that it uses appears to have never been reliable by design. SP playback & reverse search suffer from it. I've seen mid-'80s recordings made by this machine with interference from the relay not switching the heads over all the way.

Yes, I remember when head switching relays were a problem in earlier RCA/Hitachi models, as well. Back in the 90's I knew the part number for the relay by memory.

JVC started supplying hermetically sealed relays to replace those that failed. Never saw one of the sealed ones fail. Recognizable because they are solid black, not the clear cover like the originals. I remember at one point JVC started putting glue around the clear cover to try and keep the contacts from getting oxidized.

That's exactly what they did here (too bad it didn't work):

http://i.imgur.com/Cagfv4Dm.jpg

There are quite a few compatible replacements for it. I can't find any that match the dimensions (~20.5 X 11 X 12mm), though.

See this video:

https://www.youtube.com/watch?v=eYYAg965Zqk

I might have one. If I do I will send it to you. What does it say on the clear top of the relay Voltage & Ohms?

12 volts and what looks to be 310 ohms.

The one I have is a 9V version, the one they used in the JVC portable HR-2650. I suppose you could add a resistor in series with the coil and use it.

However I found some on ebay, used, but 3 mo warranty.

No affiliation btw...

http://www.ebay.com/itm/160891770319...&sojTags=bu=bu

What about this?

Looks like it should work. Not sure what the variations of the part number mean, no specs available I could find.

Then, these have a datasheet available.

The price its right but I don't know those relays. Buy one and try it! All you have to lose is $3 and the time it takes to get here from China. :yes:

**Update**:

I was wrong, the G2V-2-NV1 relay has a coil resistance of 340 ohms and does not have the voltage rating printed on it.

I purchased a pack of the HK19F 12 volt relays; they have a coil resistance of 720 ohms.

--

After installing the HK19F, removing it, and reinstalling the G2V-2, it would appear that one or more of the wires that connect the switching board to the head drum have broken. It will only turn back and forth slowly before auto returning the tape when 'play' is pressed.

Does anyone have the procedure for disassembling the head drum? The connections to the head switching board have been mended.

I have continuity between the black, brown & green wires, then the red, yellow & white wires. The drum still isn't spinning up. Which voltages should be present? I don't have the service manual.

Are you working on the head relay board or the cylinder motor? Two separate circuits. The cylinder motor I think has a plug under the deck. But without a manual I am relying on memory from repairing them 30 years ago.

I was working on the head relay board. As for the cylinder motor, yes, it does have a connector under the chassis; it connects to this power board in front of the loading mech:

http://i.imgur.com/kZmCn1Pl.jpghttp://i.imgur.com/FTjfiidl.jpg

The power board connects to the servo board which has these signals labeled:

http://i.imgur.com/zq9TQnCl.jpg

I measured the following while switching the unit from 'standby' to 'on':

"13V" - 13.19V
"12V" - 12.78V
"22V" - 25.7V

"Drum M. CTL" - 8.6V (steady)
"Drum Phase" - 6.34V (steady)

"Cap M. CTL" - peaks at 3.75V before quickly dropping to 0.65V
"Cap Discri" - 7.25V (steady)
"Cap Phase" - constantly moves between 4V and 6V

What does this tell you?

Tells me the power supply is working! But without a service manual not much else. If it was working before replacing the head switching relay I would be looking for something related, maybe a splash of solder got on the cylinder stator board, a plug partially unplugged, hard to say.