Salora SV-8800 (aka Mitsubishi HS-B10/20) VHS VCR repair - Page 1
Forum section: electronics / repair

author: kirill_maker
author_rank: Contributor
timestamp: October 20, 2023, 08:45:17 am
content: Hi all! Trying something new - fix vcr- was no power (fixed), bad rubber parts - fixed, mechanics - lubricated/cleaned.It was recaped by me - all caps (most of) was with really hi esr (some were dried up).Now I've stumbled on - why 2nd head isn't showing and not reacting to adjust of tape path (tried to re-align head drum assembly as well - but it on old place / and pick-up / take-out rolls) - maybe its dead (but I can't see cracks / damage under microscope)?Or head amp won't switch to it?Can I hook it up to video head directly - or output level will be to low for rigol dho804?On scope - fm signal synced to hall sensor in drum, head amp is usually should switch between heads, but in may can - one part is missing...Thanks!

author: wasedadoc
author_rank: Super Contributor
timestamp: October 20, 2023, 02:34:26 pm
content: I don't understand why you think one head (or its channel) has an electrical problem. As I wrote in the other thread, the heads alternate field by field. If one had a problem your picture would have alternate spatial lines looking different and the screen would be flickering at 25Hz. The TV screen photo indicates thatbothheads/channels have the same problem.

author: kirill_maker
author_rank: Contributor
timestamp: October 20, 2023, 03:50:18 pm
content: Ah, get it, message below showing that You are rightBut now I need to understand what wrong with head amp...

author: kirill_maker
author_rank: Contributor
timestamp: October 20, 2023, 04:21:48 pm
content: Ok, It seems I have signal from all heads and its nearly the same:So I guess that I need to dig inside head amp?

author: CJay
author_rank: Super Contributor
timestamp: October 20, 2023, 05:28:44 pm
content: Have you got the service manual?Salora made some really great service guides for the televisions and if they had their own for that VCR then it will also definitely help you.Mitsubishi also did really good manuals.First rule of any fault finding though, made 100% sure you haven't caused the problem yourtself, re-check all your work, make 100% certain all cables are plugged back in properly, correct socket, not trapped/pinched, cut etc.

author: kirill_maker
author_rank: Contributor
timestamp: October 20, 2023, 05:33:07 pm
content: Yes, sm for hs-b10/20 (there is no sm for sv-8800 , but they are the same) . Of course ive done something wrong, question is - whereSm contains nice adjustment part, but not troubleshooting

author: kirill_maker
author_rank: Contributor
timestamp: October 21, 2023, 02:21:53 pm
content: Still no luck, I've checked all inside head amplifier - looks ok, switching between head is working.Problem is still that part of signal is low and doesn't react to adjustment of tape path.Where I need to dig next?

author: kirill_maker
author_rank: Contributor
timestamp: October 24, 2023, 06:48:35 am
content: Ok, it's time for small update:I fixed field - problem was in wrong alignment of hall sensor magnet on moving video heads drive (I disassembled it to inspect rotary transformer), and switching was on time when head left tape edge already.The new thing is - something wrong with video signal, it's unstable and most of my capture devices are showing it as black and white...I've tried to adjust all points from service manual (switching point, noise canceling, phase of sync head, etc), but color is the problem still...SM:https://mega.nz/file/KANVCTYR#wY2np8M3exnuqAU8uOBojS8CtlnzuLgjFCxQykwJZF8

author: CJay
author_rank: Super Contributor
timestamp: October 24, 2023, 06:09:23 pm
content: Have you got an analogue monitor to try it on instead of a capture device?

author: kirill_maker
author_rank: Contributor
timestamp: October 24, 2023, 07:12:41 pm
content: Unfortunately notI know that those Chinese easy cap like devices aren't well compatible… but i have second vcr that is ok on those , and on av2hdmi device as well. So maybe there is trouble still left?

author: CJay
author_rank: Super Contributor
timestamp: October 24, 2023, 07:15:47 pm
content: Possible, can you see the disturbance on the 'scope?Look for the colour burst on the back porch of a line?

author: kirill_maker
author_rank: Contributor
timestamp: October 24, 2023, 07:40:10 pm
content: Got screenshot on scope but haven’t get it from usb still. Signal is ‘unstable’ scope can’t triger to it in video mode- line sync is glitching (for 1st look)

author: kirill_maker
author_rank: Contributor
timestamp: October 25, 2023, 06:03:56 pm
content: So, here is it:Sometimes it's in color - but only with scope connected to video test point, signal isn't stable, switching point at line sync:https://share.icloud.com/photos/0e3SvkB_MAO74FnyjdCiY9jlghttps://share.icloud.com/photos/0b18S70WHu7aYfImJYmWpsZBw

author: kirill_maker
author_rank: Contributor
timestamp: October 25, 2023, 06:50:43 pm
content: Ok, switch point was set wrong, it should be 6.5H before sync, fixed.Now - colors, maybe generator isn't set right? 4.43MHz

author: CJay
author_rank: Super Contributor
timestamp: October 25, 2023, 07:02:43 pm
content: 4.433619MHz, burned into my brain after watching a colleague try to adjust the crystal in a Sony Betamax VCR to 4.466319MHz for about 2 hours, replacing every component in the oscillator circuit and patching all sorts of capacitors to the back of the board to try and pull the crystal.He called me a bastard for not pointing out his error earlier.

author: wasedadoc
author_rank: Super Contributor
timestamp: October 25, 2023, 07:18:09 pm
content: The exact number is 4433618.75 Hz. The broadcasters maintained that to very tight tolerance, but TVs could tolerate an error of many ppm in either direction.

author: kirill_maker
author_rank: Contributor
timestamp: October 25, 2023, 07:25:15 pm
content: Well, freq meter can't show accurate (maybe its not 4.43361875)Is there possibility that quartz freq has drifted with time (35 Years)

author: kirill_maker
author_rank: Contributor
timestamp: October 26, 2023, 11:42:06 am
content: I've ordered bunch of quartz crystals (4.433619 Mhz +- 30PPM), 1 month of waiting...Maybe there is another possible problem?

author: kirill_maker
author_rank: Contributor
timestamp: October 27, 2023, 08:38:50 am
content: Ok, its fixed.Well, 1:0 in favor of the Japanese grandfathers... The polarity on the silk screen is reversed…And, its alive:I've also tried some VFD rejuvenation:Haven't pushed it alot, but its a bit brighter now, I guess not for along...

author: CJay
author_rank: Super Contributor
timestamp: October 27, 2023, 09:22:12 am
content: Nice fix and a great thread!I miss working on this old gear, it's been fun watching you work on it.

author: kirill_maker
author_rank: Contributor
timestamp: October 27, 2023, 12:40:24 pm
content: Thx, it was a long journey - to get some experience- my 1st vcrIt took me 2.5 month with mechanics clean / repair of rubber parts with 3d printer.