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Old 23rd Jun 2022, 2:03 pm   #1
Geoff 555
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Default JVC HR3660EK problems.

Hello chaps, this is the last one to bother you with I promice! Thanks to you the others have been sorted.
Now this JVC has been got at having a quick look inside, the cassette bulb is open circuit and the holder just left hanging about. The wires to the bulb has been twisted together. Measureing the voltage its 11.9 V Any kind of load and it drops to 0.0 V .
So question is what is the correct bulb please and what has been probably damaged with the wires being shorted toether?
The clock has some segments working, the head drum twitched when first powered but not now. There is nothing else happening, I have not been able to find any information so far. Worth saving, I dont know.
Ideas, help, brickbats, all welcome.
Many thanks.
All the best.
Geoff.
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Old 23rd Jun 2022, 4:50 pm   #2
G6ONEDave
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Default Re: JVC HR3660EK problems.

If memory serves the cassette lamp is 12v at between 5 to 40ma. They are not very bright to look at. The lamp terminates on the junction board (07) pins 27 and 28 which is a 2 pole plug socket, unless it's been removed.

The lamp goes between the 12v feed and base of X1 a 2SC829C which might have died due to excessive base volts. The transistor is also on the 07 junction pcb. The manual is not as clear as I would like but it appears that the junction pcb is fitted to the right of the mechanism, just follow the cassette lamp wires.

Dave
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Old 25th Jun 2022, 12:34 pm   #3
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Default Re: JVC HR3660EK problems.

Shorting out the cassette lamp was a common trick. The bulb helps the machine detect the end of a tape. When the bulb burned out, the tape functions like rewind and play all stop working. This is to prevent damage to the tape and video heads. Twisting the bulb's wires together enabled the machine to start working again temporarily, so you could see if there were any other faults and determine whether or not it's worth repairing before spending money on replacement parts.

In my experience, temporarily shorting out the cassette lamp didn't damage the electronics. You can try it to test the machine, being careful not to let a tape reach the end.

Replacement cassette lamps were available complete with the blue wires and 2-pin plug. Examples here:
https://www.donberg.co.uk/catalogue/...res/17053.html

https://www.donberg.co.uk/catalogue/...res/17050.html
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Old 26th Jun 2022, 1:37 pm   #4
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Default Re: JVC HR3660EK problems.

Hello thank you, transistor on order, shorting the wires does not do anything at all, clock and chanel tuning lamps lit. No other action!
Will order a lamp, well its a start.
Any other ideas will be welcome.
Thank you.
Geoff.
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Old 2nd Jul 2022, 12:01 pm   #5
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Default Re: JVC HR3660EK problems.

Hello thank you every one, well there is good news and bad news. The good news is that fitting the bulb and transistor brought it to life. Loads a tape and play and fast falword works, reverse does not, although the left side spindle turns (no tape) it is very weak.
There are 3 pulleys with clutches, the 2 smaller ones have quite strong springs and clamp ,the larger clutch has hardly any clamping force.
All this is possibly not that important because the picture has some major problems which may well write the thing off.
The bottom two thirds has thick bars of what I can only describe as interferance moving up from the bottom. It is not like snow.
The top third is just a band of 'interferance'.
There is no sound, from the tape, but a constant crackle.
Now and then the thick band will flick from the top to the bottom and then back to the top.
I could be wrong, I hope I am not, that this maching will go into the corner for spares probably.
Thank you again.
All the best.
Geoff.
The picture, what I can see of it is not bad but no colour.
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Old 2nd Jul 2022, 6:47 pm   #6
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Default Re: JVC HR3660EK problems.

for the picture and sound fault ,check that the pinch roller has not gone glassy upsetting the tape path. also it was quite common for the tape guides to be out of adjustment ,you need a good prerecorded tape set the tracking to the click stop and adjust the guides till the tape runs correctly .then tighten the guides with a 1.27mm allen key . the rewind issue could be just the idler tyre .
brian
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Old 3rd Jul 2022, 2:37 am   #7
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Default Re: JVC HR3660EK problems.

Are you using a old style CRT television to check it? I've had old VTRs and VCRs cause very strange interference patterns on modern flatscreens...
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Old 3rd Jul 2022, 10:14 am   #8
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Default Re: JVC HR3660EK problems.

It might be worth confirming that the tape guide roller arms are going fully into their locked positions either side of the head drum when the tape is fully laced. They may appear to be correct but they should be locked and not movable. I mention this as the problem might be down to the loading mechanism not going all the way. That could be due to dry grease, bent levers or a timing issue due to incorrect meshing of the drive gears. The mechanism will need a good dose of looking at and checking against the service manual images. Remember it only takes one tooth to be out of it's meshed position.

Dave
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Old 4th Jul 2022, 10:18 am   #9
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Default Re: JVC HR3660EK problems.

Hi all, many thanks for your help. G6ONE Dave Hello Dave yes the tape guide roller arms are going home and are fully locked.
John116 I am using a old CRT television.
gallowfields Hi I have a good pre recorded tape. The tracking control will be set to the click stop. I will try to give the guides a tweek, now asking a silly question why is it common for the guides to be out? Thanks Brian.
It will be a little time ,next week, until I can get to it, but I will be back.
Thank you again for your help.
Geoff.
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Old 4th Jul 2022, 10:32 am   #10
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Default Re: JVC HR3660EK problems.

At the base of each guide there is a small grub screw that locks the guide central shaft and these tiny screws have a habit of coming loose, thereby losing their grip to the centre shaft. After that due to the friction of the tape moving over the guide rollers, the whole guide assy can sometimes rotate and thus changing the tape path height and hence the tracking problem. Several tape machines can suffer with this issue, not just yours. Once you have everything set correctly you could try a drop of thread lock adhesive to try a prevent a repeat of the problem.

Something else that I've come across is wear and tear on the rollers causing them to wobble on their centre shaft. Also sometimes the roller can stop rotating freely on it's shaft, causing tape friction to turn the whole assy instead of just the roller.

Dave
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Old 4th Jul 2022, 1:26 pm   #11
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Default Re: JVC HR3660EK problems.

Quote:
Originally Posted by Geoff 555 View Post
Hi all, many thanks for your help. G6ONE Dave Hello Dave yes the tape guide roller arms are going home and are fully locked.
John116 I am using a old CRT television.
gallowfields Hi I have a good pre recorded tape. The tracking control will be set to the click stop. I will try to give the guides a tweek, now asking a silly question why is it common for the guides to be out? Thanks Brian.
It will be a little time ,next week, until I can get to it, but I will be back.
Thank you again for your help.
Geoff.
it was quite common with a lot of vcr,s for the tape guides to move ,most are secured at the base with either a small screw or an allen screw [1.27mm] was popular the exception was mitsubishi that did,nt use anything so we used loctite on those after resetting them. .be very careful when adjusting them to see the tape following along the edge of the lower drum and then you will not be far out. .try a few prerecorded after adjustment just to check
regards brian
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Old 5th Jul 2022, 1:34 pm   #12
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Default Re: JVC HR3660EK problems.

Hi all many thanks, have just spent 1.5 hours checking everything, very carefully tried to adjust the guides and the bars that were rolling up from the bottom are now just a couple of thin stationary bars.
The 2.5" deep band accross the top of the picture remains unaffected, still a crackle on sound and no colour.
So this one is going to be sat in the corner in disgrace until I can spend more uninterupted time on it.
While I think of it the tracking and slow motion controlls do nothing.
Thank you again.
All the best.
Geoff.
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Old 5th Jul 2022, 4:12 pm   #13
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Default Re: JVC HR3660EK problems.

Is the tape central height wise on the ACE head (audio/control head) and is the arm that pulls the tape to out from the cassette going to full position? Also is the ACE head vertical both sidewise and forward/backwards? Too much tilt on the ACE head could well cause issues.

It might be worth checking continuity on the screened leads between the ACE head and the pcb where they connect to. Also check for dry joints on their soldered receptacles.

An oscilloscope would be useful here to check that you are getting control track pulses from the ACE head.

Dave
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Old 5th Jul 2022, 6:32 pm   #14
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Default Re: JVC HR3660EK problems.

Or unplug the control head and see if things change for the worse, or not.
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Old 6th Jul 2022, 4:26 pm   #15
Geoff 555
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Default Re: JVC HR3660EK problems.

Hello, gentlemen I am back again for the last time, connected up and checked the test signal was tuned in OK. Loaded a tape and it was as before.
Turned round for a screwdriver, head torch etc. turned back to find that the screen was just filled with snow and no sound (crackle).
So I am calling it a day. Lifting it up and down off the dining room table, its the only space I have got at the moment, is too much for my back.
So thanks everyone.
Cheers.
Geoff.
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