JVC HRD-370 - various faults - UK Vintage Radio Repair and Restoration Discussion Forum

AidanLunn · 21st Aug 2012, 9:47 pm

Hello all. How's about this one for a challenge? Forget JVC-built decks not wanting to wake up or Panasonic D1 mode switches needing to be cleaned, this one is a real head-scratcher!

A bit of an intro for those who can't remember, the HRD-370 is a HiFi deck, introduced in 1986, no NICAM, that was designed to be the next JVC mech's equivalent of the HRD-725, an image of one is here:

http://wegavision.pytalhost.com/jvcHRD370EG/jvc01.jpg

This one has exhibited 3 very odd faults:

1) Lack of colour on playback. Colour is present through E-E and on its own recordings but on any tape from any other machine? Not a trace of colour. On a tape blanked with blue screen from a Samsung deck I had ages ago, there were flashes of orange colour, and there is a flash of colour on f/f search just as the capstan is gearing up to faster speed.

2) HiFi audio - again it will play fine on its own recordings, but on other machine's recordings, it will only be heard when the tracking is adjusted to give noise on the picture.

3) I haven't had much time to check today as my FV33, still in pieces, is taking up most of my desk space, but when in play/record mode, , after about 15 minutes, a whining can be heard from within equivalent in pitch to the old tone that accompanied Test card F and then the machine unlaces.

i realise of course that whatever is causing the whining may also be the cause of the other two faults, or a plug may be in the wrong way round or the head drum leads may be soldered incorrectly, but I'd like to ask other members here of any other possible causes of this very odd fault.

Obviously, it'd be a good idea to check the output of colour bars with my scope, but I've never had the chance to learn how to use it yet.

Best regards,
Aidan Lunn

HamishBoxer · 21st Aug 2012, 9:53 pm

IF its not been "got at",it might be worth checking for high esr caps in power supply as they do give oddball faults.

Maarten · 21st Aug 2012, 10:14 pm

If it has been got at, check for the head drum being mounted the wrong way around (180 degrees) if that's physically possible on this model. This will give symptoms very much like yours. On the picture anyway, I never checked this on a hifi machine.

Alternatively, the head servo may be out of phase.

AidanLunn · 23rd Aug 2012, 9:28 am

The head being mounted the wrong way round is what I first thought

There is one other fault I've noticed with the LED audio meters:
X they are always switched on (even when in standby - is that normal?)
X they're always picking up some kind of noise to light the first few LEDs on both bars
X and the current to the LED display actually interferes with them- when the clock is flashing "00:00", the levels on the meters rise slightly when off, and dip slightly when on - decoupling capacitor somewhere?

nickdoofah · 23rd Apr 2013, 2:31 am

certainly sounds like the drum being 180 degrees out!

as above though, i'm not sure where a hifi machine is concerned!

Maarten · 23rd Apr 2013, 11:45 am

I missed Aidan's last message. He might be on to something too when mentioning 'decoupling capacitors'. Interference (from the power supply) can also cause such symptoms.

21st Aug 2012, 9:47 pm	#1
AidanLunn Heptode Join Date: Jan 2010 Location: Killamarsh, Sheffield, South Yorkshire, UK. Posts: 746	JVC HRD-370 - various faults Hello all. How's about this one for a challenge? Forget JVC-built decks not wanting to wake up or Panasonic D1 mode switches needing to be cleaned, this one is a real head-scratcher! A bit of an intro for those who can't remember, the HRD-370 is a HiFi deck, introduced in 1986, no NICAM, that was designed to be the next JVC mech's equivalent of the HRD-725, an image of one is here: http://wegavision.pytalhost.com/jvcHRD370EG/jvc01.jpg This one has exhibited 3 very odd faults: 1) Lack of colour on playback. Colour is present through E-E and on its own recordings but on any tape from any other machine? Not a trace of colour. On a tape blanked with blue screen from a Samsung deck I had ages ago, there were flashes of orange colour, and there is a flash of colour on f/f search just as the capstan is gearing up to faster speed. 2) HiFi audio - again it will play fine on its own recordings, but on other machine's recordings, it will only be heard when the tracking is adjusted to give noise on the picture. 3) I haven't had much time to check today as my FV33, still in pieces, is taking up most of my desk space, but when in play/record mode, , after about 15 minutes, a whining can be heard from within equivalent in pitch to the old tone that accompanied Test card F and then the machine unlaces. i realise of course that whatever is causing the whining may also be the cause of the other two faults, or a plug may be in the wrong way round or the head drum leads may be soldered incorrectly, but I'd like to ask other members here of any other possible causes of this very odd fault. Obviously, it'd be a good idea to check the output of colour bars with my scope, but I've never had the chance to learn how to use it yet. Best regards, Aidan Lunn Last edited by AidanLunn; 21st Aug 2012 at 9:53 pm.

21st Aug 2012, 9:53 pm	#2
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: JVC HRD-370 - various faults IF its not been "got at",it might be worth checking for high esr caps in power supply as they do give oddball faults. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

21st Aug 2012, 10:14 pm	#3
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: JVC HRD-370 - various faults If it has been got at, check for the head drum being mounted the wrong way around (180 degrees) if that's physically possible on this model. This will give symptoms very much like yours. On the picture anyway, I never checked this on a hifi machine. Alternatively, the head servo may be out of phase.

23rd Aug 2012, 9:28 am	#4
AidanLunn Heptode Join Date: Jan 2010 Location: Killamarsh, Sheffield, South Yorkshire, UK. Posts: 746	Re: JVC HRD-370 - various faults The head being mounted the wrong way round is what I first thought There is one other fault I've noticed with the LED audio meters: X they are always switched on (even when in standby - is that normal?) X they're always picking up some kind of noise to light the first few LEDs on both bars X and the current to the LED display actually interferes with them- when the clock is flashing "00:00", the levels on the meters rise slightly when off, and dip slightly when on - decoupling capacitor somewhere?

23rd Apr 2013, 2:31 am	#5
nickdoofah Banned Join Date: Jan 2009 Location: Littlehampton, West Sussex, UK. Posts: 142	Re: JVC HRD-370 - various faults certainly sounds like the drum being 180 degrees out! as above though, i'm not sure where a hifi machine is concerned!

23rd Apr 2013, 11:45 am	#6
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: JVC HRD-370 - various faults I missed Aidan's last message. He might be on to something too when mentioning 'decoupling capacitors'. Interference (from the power supply) can also cause such symptoms.