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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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24th Sep 2016, 1:43 pm | #1 |
Hexode
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
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JVC HR-7700EK no display
Hi,
Managed to get one of these machines and it's nice and clean inside and out. Problem is there is no display at all, the lights for the tuner and Dolby noise reduction work and you can hear the eject motor run for a second. It won't accept a tape despite the mechanism and belt seeming ok. Guess I need to get the display working first. Have checked all connections and it seems ok. Is there anything that fails on these to cause this symptom? Thanks Steve Last edited by Vauxfan2k; 24th Sep 2016 at 1:53 pm. |
24th Sep 2016, 1:59 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,740
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Re: Jvc hr-7700EK no display
Have you checked all the fuses? There are sometimes tiny soldered in ones as well as the more obvious ones.
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24th Sep 2016, 6:36 pm | #3 |
Heptode
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
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Re: JVC HR-7700EK no display
I have the same machine with the same problem! The DC-DC converter has failed and needs to be replaced.
Fivos |
24th Sep 2016, 9:08 pm | #4 |
Hexode
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
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Re: JVC HR-7700EK no display
Chances of finding one of them on its own eh? Well if I ever get another machine that's working il change the fascia etc over and break it for bits.
Only cost beer money anyways. |
25th Sep 2016, 2:09 am | #5 |
Heptode
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
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Re: JVC HR-7700EK no display
A Ferguson 3V23 which is pretty common in the UK would be good for a parts machine. Mine is the AKAI version. The rubber rollers on the cassette carriage may be dried out and don't have enough grip to drag the cassette into the loading mechanism or simply the belt is worn.
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25th Sep 2016, 9:48 am | #6 |
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,666
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Re: JVC HR-7700EK no display
Can we see the circuit diagram for the DC-DC converter? If it's generating about 30V to power the vacuum fluorescent display, it might be possible to replace it with one of the cheap boost converter modules now widely available on eBay and the like.
Chris
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25th Sep 2016, 10:03 am | #7 |
Hexode
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
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Re: JVC HR-7700EK no display
if it's like a 3V31 the converter also supplies the AC to the display heater.
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25th Sep 2016, 10:16 am | #8 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: JVC HR-7700EK no display
Not all DC-DC converters are potted solid in resin; some of them can be repaired.
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25th Sep 2016, 10:23 am | #9 |
Hexode
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
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Re: JVC HR-7700EK no display
they are not potted. It's a long time since I saw one but I think it's a single transistor, a couple of zeners, a fusible resistor a small transformer and a few other parts. Access was the bigger problem
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25th Sep 2016, 12:42 pm | #10 |
Hexode
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
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Re: JVC HR-7700EK no display
having thought about this a bit more the DC-DC converter on it's own is not going to stop it accepting a tape and working normally. It is possible a supply line is missing to the display driver/ controller or there is a fault elsewhere. ( if the converter is working you may be able to see the heater filaments in a darkened room)
It would also be worth checking the cassette lamp |
25th Sep 2016, 1:40 pm | #11 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
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Re: JVC HR-7700EK no display
The fuses look similar to BC147 type LockFit transistors.
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25th Sep 2016, 3:20 pm | #12 |
Dekatron
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Location: W.Butterwick, near Doncaster UK.
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Re: JVC HR-7700EK no display
Sorry I should have said BC147 type Not LockFit!
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25th Sep 2016, 3:49 pm | #13 |
Hexode
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
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Re: JVC HR-7700EK no display
I can wind the tape in manually by rolling the motor with my finger. Even when fully insterted it won't attempt to rewind/ff or play. Altho if I switch the machine off and back on it ejects the tape no problem.
I've had to put it on the back burner for now as I have another machine that I'm working on. I was never really that interested in the 3v23 or its variants, just didn't float my boat, perhaps that's affecting my lack of enthusiasm for working on it lol. |
25th Sep 2016, 10:20 pm | #14 |
Heptode
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
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Re: JVC HR-7700EK no display
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30th Sep 2016, 10:55 pm | #15 |
Heptode
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
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Re: JVC HR-7700EK no display
I also found this gem:
http://www.ebay.co.uk/itm/ferguson-3...torefresh=true |