'Shadow' on VHS machines playing 405 - UK Vintage Radio Repair and Restoration Discussion Forum

Panrock · 29th Mar 2017, 12:30 pm

I bought my first VHS machine in 1982. It was a Fisher FVH-530 (if I recall the number correctly) and lasted for twenty years of regular use until it got 'sluggish'. I was then given a JVC HR-D180EK, which I have to this day and still works well enough. You may gather from this I have never got into servicing video recorders!

I have used both machines with my collection of 405-line VHS tapes. The picture is very sharp due to the less stringent bandwidth requirement on 405. Sometimes, on worn tapes the incorrect dropout compensation timing can be a pain, but I think of this like 'ignition interference'.

On the later JVC machine, there is a faint shadow two-thirds across the picture. This is where the machine presumably expects the next 625-length line to begin.

What internal feature is causing this? Has anyone done a survey of which machines do and do not exhibit this effect? Can anything be done about it? It never seemed to be reported on the early machines.

Steve

1100 man · 29th Mar 2017, 3:31 pm

Hi there,
I recently experimented with a Ferg 3v29 vcr to record and play 405 material. There was a very noticeable shadow on playback. Gave a very good impression of 'Ghosting' though- quite authentic!
After a bit of experimenting and a look at the circuit, it turned out to be the drop out compensator circuit getting confused. I just grounded the input to the DOC input on one of the signal processing chips and it all worked very well.
If you need exact details, I will dig out the manual.
I can't rightly remember if my 3v22 did the same but I don't think it did. I don't think it has a DOC anyway.
Certainly my CV2100 ACE works (or used to before it spent 10 years in the barn) perfectly on 405.
Cheers Nick

60 oldjohn · 29th Mar 2017, 4:53 pm

I had ghosting similar to Steve on a Ferg 3V31, 3 or 4 years ago so nearly forgotten but I seem to remember this was to be expected.

John.

29th Mar 2017, 12:30 pm	#1
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,532	'Shadow' on VHS machines playing 405 I bought my first VHS machine in 1982. It was a Fisher FVH-530 (if I recall the number correctly) and lasted for twenty years of regular use until it got 'sluggish'. I was then given a JVC HR-D180EK, which I have to this day and still works well enough. You may gather from this I have never got into servicing video recorders! I have used both machines with my collection of 405-line VHS tapes. The picture is very sharp due to the less stringent bandwidth requirement on 405. Sometimes, on worn tapes the incorrect dropout compensation timing can be a pain, but I think of this like 'ignition interference'. On the later JVC machine, there is a faint shadow two-thirds across the picture. This is where the machine presumably expects the next 625-length line to begin. What internal feature is causing this? Has anyone done a survey of which machines do and do not exhibit this effect? Can anything be done about it? It never seemed to be reported on the early machines. Steve __________________ https://www.radiocraft.co.uk

29th Mar 2017, 3:31 pm	#2
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: 'Shadow' on VHS machines playing 405 Hi there, I recently experimented with a Ferg 3v29 vcr to record and play 405 material. There was a very noticeable shadow on playback. Gave a very good impression of 'Ghosting' though- quite authentic! After a bit of experimenting and a look at the circuit, it turned out to be the drop out compensator circuit getting confused. I just grounded the input to the DOC input on one of the signal processing chips and it all worked very well. If you need exact details, I will dig out the manual. I can't rightly remember if my 3v22 did the same but I don't think it did. I don't think it has a DOC anyway. Certainly my CV2100 ACE works (or used to before it spent 10 years in the barn) perfectly on 405. Cheers Nick

29th Mar 2017, 4:53 pm	#3
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,985	Re: 'Shadow' on VHS machines playing 405 I had ghosting similar to Steve on a Ferg 3V31, 3 or 4 years ago so nearly forgotten but I seem to remember this was to be expected. John.