Questions: JVC KD-V6 operation/troubleshooting

After doing some research on "best 3head decks" and "if not Nakamichi" and "easiest to maintain decks", i bought a JVC KD-V6. Supposedly from "original owner", not running but not maintained either. This is supposed to be a deck that "hits well above it's price point" and is pretty reliable and easy to maintain.

First thing i did, the tape detection leaf switches were not working, so every tape was "Metal", which is not going to give good results. So those work good now.


I checked belt, and noticed the belt was still working, capstan running when tape inserted (good).
However the head block won't lift/engage the heads when push PLAY, FF and RW don't work...

Then I noticed an interesting point: when you initially power on the unit, the LEVEL Meter and PEAK meters are at "0db", which is correct.


but after about 1 second, the VU meter goes to 3db, and the peak measure goes to 4db. No buttons pushed, nothing moving, tape in or out.


Whatever is keeping the deck from running is also making these meters show false indication, too.
Is anyone familiar enough with these decks to help ID root cause, of direct me where to look?
I've checked for loose wires or anything else inside, didn't see anything. Deck actually looks very clean inside and out.

Last question: has anyone removed this recording volume slide switch knob? looks like it should pull straight out?


Thanks, experience appreciated!

 

Power supply problems ?
A tip. If you start dismantling note very carefully where everything goes (photos and labeing cables helps).
Not that I have ever turned a half functioning Technics deck into a not functioning at all one by not doing that

 

I went and looked, interesting... i measure 110v line to the transformer,but look at these solder points...
I will check diagram and see what voltages it's supposed to provide, to see if it's working... seems like it's seen some heat!
might just re-solder the main points

 

i resoldered terminals, had to help... rosin actually bubbled out from under some of the joints!
then i measured voltages: two at one end (S1 & S2)measured about 9v, two outer ones on other side measured about 11v (connect to S4 & S5 through diodes), but the S3 terminal in between the 11v measured 0v... It looks like a common point, not sure what it's supposed to measure.
these outputs are marked S1,S2,S3,S4, S5


looking at the SM having a hard time determining what voltage should be... zero might be correct ...

(JVC Shop Manual image, courtesy HiFiEngine archives, https://www.hifiengine.com/manual_library/jvc/kd-v6.shtml)

 

Surprise Success!
After I re-soldered and cleaned up the solders at the transformer yesterday evening, I thought I checked deck operations, and didn't see any improvement... I thought.

This morning I put in a Maxell XLII in to make sure the tape detector was still working OK, and just for the heck of it hit play, and it started running!

Earlier it wouldn't FF/REW or even couldn't lift the headblock... now, magically, it's running!!
The odd thing, I accidentally left it powered on overnight, no tape in it, just power on... unless I didn't check it well after I resoldered. Now it's got me wondering if that resolder did the trick!! I'm gonna credit that! Thanks @Longman!!

The VU meters are still stuck at the +3db, and the "Max" reads no less than 4db, but when the tape or level goes above those values, it shows up!! Just no lower.
The channels seem balanced, good highs and lows, Dolby B/C seems to work fine, sounds really great!! Just the VU meters now...
I recorded a tape; Eagles "Greatest hits" on one side, B-side Steely Dan "Can't Buy a Thrill" and a song from "Pretzel Logic", the tape sounds awesome on Walkman, too! So recording great! meter just a bit of a pain...

Since it's open, I did run Alex /A.N.T's "WFGUI program by Alex Freed " just to make sure... Initially it was running at 3073!! so I adjusted to ~3005... I'll check it again tomorrow to make sure it holds... W/F running about .09-.10, which is high, but the spec for this deck is max .08, so not surprised.

The sound for the deck is super: very wide range, excellent bass, full midrange, and excellent highs! Steely Dan uses chimes in a couple songs, and they come through super clearly! Great channel separation too... with those poor solders, wonder if the original owner had trouble with it and didn't use it much!

Thanks for looking, and thanks for the help @Longman ! Now to move on to the meters...

Thanks so much for the suggestion @Longman, I would not have even thought to look at that power circuit!!

 

Day 3
Checked speed, still running 3005-3007, even warmed up, various parts of test tape. W/F still hovers .09-.10
Removed transformer to clean, check and resolder all coil connections: they look better, but no change in operation.
The two small lines on the PCB mounted to transformer are actually thermal fuses, not diode... duh... special wire that will melt with excess current. OK
Cleaned several wire harness and connections that run from various areas of PCB to the meter board, but still have meters resting on +3db, +4db peak

So deck running and recording fine, just issue with "stuck" meters.

Closing it up and will enjoy it for a while!

 

Hi - I've had badly behaving meters on a Pioneer CT91 (arguably another potential Nakamichi alternative but the mech is challenging) that I fixed by air-cleaning behind all of the front panel switches.
To be clear, none of the transport or other switches is mechanical, it's all electronic. I guess that after a lifetime of dust gets in and around the contacts, anything can happen. Worth a try anyway.
Cheers.

 

I'll try the air cleaning for those front switches! Thanks
Yes your CT-91 was definitely mentioned on the "best of the 3-head" and "If not Nakamichi" list! That Elite Pioneer series (90-95) were all listed!
Thanks @DutchNick

 

Hey @Dfcruiser, can you tell me a little about how you fixed your leaf switches? My deck is stuck on "metal." I'm not even sure if I've found my switches because I'm not too familiar with these. Is that what you've highlighted in your 2nd pic? Did you simply spray contact cleaner on them, or did you totally disassemble?

Btw, I also had to re-flow my transformer. Fixed the main display not working! And I ended up stupidly breaking my slider trying to get it back on

 

@scintor : Do you have a copy of the shop manual for the V6? that helps some.
the switchs are located along the top of the cassette mechanism: when you remove the cover, they are lined up right along the top (there are 4, I just highlighted 3):


They are "micro switch" type, the shop manual says each held in with a tiny screw, I believe i was able to move and clean them without removing the entire mechanism, but not 100% on that. Be careful to wiggle out as they are partly under the black plastic faceplate.



you most likely have some contacts "stuck" together... I spray with deoxit red, then use a paper "post-it" to separate and clean the contacts. spray the paper with deoxit too, rub back and forth to help clean.
you do not want to force the contacts open too much, or you might bend the copper leaf. I remember it was a tight area to work in.

Did I read that right, when you re-flowed solder the main display started working right? I wasn't as lucky: deck works great, except that display still doesn't go to zero. Did you get the slider knob off by prying up? I tried, but didn't want to force too hard, so never removed. I wanted to check solder connections on the board for the meters, but couldn't get to it!

hope this info helps.

 

Thank you! Huge help. Would you be able to link the service manual? Hi Fi Engine no longer accepts new registrants! Or send?

Yeah! The vacuum fluorescent display didn't work at all. I actually opened it up to check the solder connections on the board, too (and the slider just popped off because I was too dumb to remember that it would-- however, I actually broke it trying to put it back on! it was very brittle). Then I looked up a youtube video about common problems with VF displays, and dude said it's usually power delivery. Which made sense because my deck was clean as a whistle inside (a nice benefit of a completely enclosed deck). Looked at my transformer, and sure enough, bad contacts. Reflow of just one obvious bad joint fixed it right away. Your counter issue sounds a bit separate from this, honestly.

Curious, when you put type 2 cassettes in, does it detect CrO2 or no because it's only pseudochrome?

 

Closer view ot the micro switch:


I cleaned mine in place, so I had to remove the screws and wiggle the switch out from under the plastic face plate.

 

@scintor : did you reflow solder at the meters? or just at the power supply? Mine was very clean, and came from an original owner, so it was very clean inside and out. But those solder joints looked terrible at the transformer... I've read JVC often had bad solders.

One thing to check, if you clean contacts and you are still stuck on Metal, check to make sure your switch isn't somehow bent so the contacts can't open. You should be able to inspect that they open and close when you remove them.

 

Thank you so much for that photo! super helpful.

So far, I only saw one broken joint, on the transformer, and I reflowed that and everything magically worked (the transport did work previously). So I'm going to go in and reflow all joints.

My PCB joints looked pristine. There was one 3-wire terminal that looked like it could have been iffy, so I reflowed that first, but it didn't help. Only next did I try the transistor.

 

@scintor: I have heard HiFiEngine (and VinylEngine) appears not to be accepting new members, too bad there is so much reference materials there:
Other places to look for various manuals: https://elektrotanya.com, https://freeservicemanuals.info/en/, https://www.manualslib.com, http://akdatabase.com/AKview/index.php

I tried to upload shop manual but it's too large... 32.5meg... do you have an ftp or drop box?

Here is owners manual, though it doesn't have drawings or diagrams

 

@scintor Broke SM into 4 sections, easiest way to get it to you:

 

THANK YOU! I really appreciate that because I had looked at a few other sites to no avail. Cheers.

 

Not just they are not accepting new members (and probably never will), but they are deleting accounts without any explanation.
I recently needed to download some service manuals and realised my account was deleted, account which I had for many years.
Which is unfortunate because if such a resource is meant only for insiders, there's little value it provides to the tape/HiFi community at large apart from the specs that are publicly available.

 

@Valentin : I'm sad to hear that happening! Is there anything specific I can help you look for?
In the last 5 years I've uploaded over 100 documents, I certainly hope I don't get booted! There are some documents I have not been able to find anywhere else! @MisterX can find items on "archive.org", which I just have not figured out how to use.
Let me know if theres something I can search for you.

 

Thanks for the offer, appreciate it ! At the moment I don't need anything, but will ask in the future if in need.

Given this I don't think there's any risk at all, as you're a valuable member of the community. I never uploaded any documents, not sure if I needed to do so in order to stay active.
Maybe that is why they deleted my account and if so I am at fault.