MCI JH-110 issues

[CurtZHP]

Does anyone here have any experience with MCI JH-series machines?

I have an MCI JH-110 that I suppose is beginning to show her age.

Fired her up for the first time in a long while and racked up an alignment tape.  Ran into a couple hopefully minor issues.
1.  The high-frequency repro adjust on the right channel basically tops out well below 0VU (around -7).  I swapped repro cards between channels and the problem stays with the right channel, so I might be able to rule out the card.
2.  There seems to be an intermittent issue with the tape counter freezing up.  At some point the numbers stop counting and none of the controls for that work at all.  A power cycle appears to fix the issue for a while.

Fortunately, I have the complete service manual for the machine, but I thought before I dive too far into its guts, I'd see if anyone else had some tips first.

 

[buildafriend]

2.  There seems to be an intermittent issue with the tape counter freezing up.  At some point the numbers stop counting and none of the controls for that work at all.  A power cycle appears to fix the issue for a while.

Following since a friend is having a similar issue on an Otari. Are there Electrolytics or Tantalum caps on the board that controls this? I'm shooting in the dark there but maybe?

Also, if the issue follows the card I might also recap that card and check the trimmer. It could be the amps too.. Yet again - shooting somewhat blindly there.

 

[CurtZHP]

Following since a friend is having a similar issue on an Otari. Are there Electrolytics or Tantalum caps on the board that controls this? I'm shooting in the dark there but maybe?

Also, if the issue follows the card I might also recap that card and check the trimmer. It could be the amps too.. Yet again - shooting somewhat blindly there.

That was my first suspicion, that some boards may just need to be recapped.  The issue does NOT follow the repro card, so it's got to be further upstream.  Planning to crack open the manual tonight or tomorrow.

 

[CurtZHP]

Messed around with it a little more today.

I found that simply thumping the machine in a few places got it to behave sometimes, and sometimes not.
After a little of this "percussive maintenance," I actually did get the initial problem with the high frequency calibration to disappear.

So, at this point, I'm thinking that several of the card connections are just oxidized, and a thorough cleaning with some contact cleaner is in order before going any further.

 

[Rob Flinn]

I would look at the molex connectors, reflow the solder round them.

 

[buildafriend]

Yeah and maybe use some isopropyl electronics cleaner on the pins

 

[RSRecords]

counter: check counter accuracy cap under deck. Also, check that the roller to the left of the head stack is clean on the bottom. Caps on the RTZ can cause issues too.

audio: swap the head connectors to see if it follows the head.
Turn the MRL over to see if its the tape.

 

[CurtZHP]

So, I finally had a chance to work on this again.  Took the guide roller to the left of the headstack off and shot some canned air in there, paying close attention to the photocell under there.  That seems to have taken care of the tape counter issue.

Now to systematically clean all the card pins inside.