UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 24th Sep 2016, 1:43 pm   #1
Vauxfan2k
Hexode
 
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
Default 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
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	174
Size:	55.6 KB
ID:	130479  

Last edited by Vauxfan2k; 24th Sep 2016 at 1:53 pm.
Vauxfan2k is offline  
Old 24th Sep 2016, 1:59 pm   #2
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,740
Default 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.
paulsherwin is offline  
Old 24th Sep 2016, 6:36 pm   #3
dj_fivos_sak
Heptode
 
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
Default 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
dj_fivos_sak is offline  
Old 24th Sep 2016, 9:08 pm   #4
Vauxfan2k
Hexode
 
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
Default 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.
Vauxfan2k is offline  
Old 25th Sep 2016, 2:09 am   #5
dj_fivos_sak
Heptode
 
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
Default 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.
dj_fivos_sak is offline  
Old 25th Sep 2016, 9:48 am   #6
cmjones01
Nonode
 
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,666
Default 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
__________________
What's going on in the workshop? http://martin-jones.com/
cmjones01 is online now  
Old 25th Sep 2016, 10:03 am   #7
tony brady
Hexode
 
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
Default Re: JVC HR-7700EK no display

if it's like a 3V31 the converter also supplies the AC to the display heater.
tony brady is offline  
Old 25th Sep 2016, 10:16 am   #8
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: JVC HR-7700EK no display

Not all DC-DC converters are potted solid in resin; some of them can be repaired.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline  
Old 25th Sep 2016, 10:23 am   #9
tony brady
Hexode
 
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
Default 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
tony brady is offline  
Old 25th Sep 2016, 12:42 pm   #10
tony brady
Hexode
 
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
Default 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
tony brady is offline  
Old 25th Sep 2016, 1:40 pm   #11
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,923
Default Re: JVC HR-7700EK no display

The fuses look similar to BC147 type LockFit transistors.
__________________
G8JET BVWS Archivist and Member V.M.A.R.S
HamishBoxer is online now  
Old 25th Sep 2016, 3:20 pm   #12
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,923
Default Re: JVC HR-7700EK no display

Sorry I should have said BC147 type Not LockFit!
__________________
G8JET BVWS Archivist and Member V.M.A.R.S
HamishBoxer is online now  
Old 25th Sep 2016, 3:49 pm   #13
Vauxfan2k
Hexode
 
Join Date: Aug 2016
Location: Inverness, Highland, UK.
Posts: 300
Default 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.
Vauxfan2k is offline  
Old 25th Sep 2016, 10:20 pm   #14
dj_fivos_sak
Heptode
 
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
Default Re: JVC HR-7700EK no display

http://freeservicemanuals.info/en/se.../Ferguson3v23/

Grab the service manual from here.
dj_fivos_sak is offline  
Old 30th Sep 2016, 10:55 pm   #15
dj_fivos_sak
Heptode
 
Join Date: Mar 2015
Location: Lefkada, Greece
Posts: 969
Default Re: JVC HR-7700EK no display

I also found this gem:
http://www.ebay.co.uk/itm/ferguson-3...torefresh=true
dj_fivos_sak is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:13 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.