If you have an MCI JH110, I need your help

[nosebleedaudio]

What are you measuring it with?
Has this happened recently?
Are you hitting the tape hard?

[Brad McGowan]

I'm measuring bias frequency with a brand new frequency counter. I'm measuring AC voltages with a Fluke multimeter.

As far as I know the erase has never been right as long as I owned the machine....since June.

To test and set the erase peak I am recording a 500Hz tone onto the tape at 0VU = +3/355 nWb/m, so no, I'm not hitting the tape hard. Then while monitoring the playback I record nothing over that tone and listen in headphones as I turn the erase peak trimmer on the audio motherboard until the 500Hz tone disappears the maximum amount.

I just need a sanity check on what the voltage should be at that trimmer cap. The manual states I should get 60-70 V RMS when R9 trimmer on the oscillator board is fully clockwise. I can't get more than 40-45 V.

thanks,
Brad

[nosebleedaudio]

Unless it is a special Fluke it may not accurately measure High frequency.
If you have a scope that will be more accurate.
From memory the MCI needs that frequency to be very close to spec..

[Brad McGowan]

I'm not measuring frequency with the Fluke multimeter. I'm measuring frequency with a dedicated frequency counter which is accurate to 0.1Hz at 120kHz. Are you saying that it's inaccurately measuring the voltage because it's a high frequency AC signal? That would seem to explain why the manual says to hook up an oscilloscope.... Doh!

Another thing to note is that I recently had the heads relapped by JRF. I have been staying away from adjusting the erase head wrap, but perhaps I need to tweak it?

thanks,
Brad

[David Kulka]

I used to work on these machines a lot...I'm not near a manual at the moment and don't exactly recall the electrical side of the alignment procedure, but here are some thoughts that might help...

Many DVM's and VOM's will not measure the bias frequency accurately. Check the specs of your meter. It's possible that the voltage is fine, but your meter just reads low because it's not meant for high frequencies. I used to use wideband analog AC voltmeters for this tweak. You can certainly use a scope but it will show you peak to peak voltage and you would have to multiply by .7 to convert to RMS.

Did the machine erase ok before the heads were relapped? Was the erase head relapped? Does one track erase ok, and not the other?

It's very possible that you need to adjust the erase head wrap. It's not terribly critical or difficult to do. Just record a few minutes of tone and then erase it while monitoring repro. Adjust wrap for deepest erasure. Make sure that the height and azimuth are correct too. You can probably get a good idea just by eyeballing it carefully.

[Brad McGowan]

I'm looking into getting an oscilloscope...I really should have one already. Thanks for the tip about multiplying by 0.7 for RMS.

I'm not really sure if the machine was erasing properly before the heads were relapped since I sent the heads in the day I got the machine. I'd have to check the head report to see if the erase head was relapped. My gut tells me that it was not. All the channels seem to erase about the same amount.

thanks,
Brad

[nine99nine]

Try Chris Mara or his associate Matt. They work on tons of MCI gear (especially their tape machines) and are always knowledgeable! They should get back to you pretty quick via email.

cym@mindspring.com - Chris Mara email
mattvallen@gmail.com - Matt Allen email

[nosebleedaudio]

Peak to peak is divide by 2 first then *.707

[nosebleedaudio]

Originally Posted by Brad McGowan

I'm looking into getting an oscilloscope...I really should have one already. Thanks for the tip about multiplying by 0.7 for RMS.

I'm not really sure if the machine was erasing properly before the heads were relapped since I sent the heads in the day I got the machine. I'd have to check the head report to see if the erase head was relapped. My gut tells me that it was not. All the channels seem to erase about the same amount.

thanks,
Brad

The old grease pencil works good for this, as far as wrap goes.
A scope will also allow you to see the sine wave, if it's clean, no distortion, clipping ect...

[Brad McGowan]

Thanks for the tips guys. I really appreciate it.

Brad

[soupking]

Originally Posted by Brad McGowan

My damn MCI JH110 is driving me crazy. I can't seem to get it to erase as deeply as it should and I'm stuck. If you have one of these decks...2, 4, 8 track, doesn't matter...I desperately need your help. Can someone please measure the RMS AC voltage on the left tab of the erase peak trimmer C1 on the audio motherboard while recording and tell me what you get? I think it's "point C" on the motherboard schematic in the manual. The manual says that I should be able to get 50V RMS. I'm getting more like 40V, and I still hear the old tracks on the tape when recording over them.

Someone please help before I push this thing off a cliff.

thanks,
Brad

I've been having similar issues with my JH24. We got out an oscilliscope and re-caled the master bias oscillator. That seemed to work. Then we re-biased/High-EQ'd it and the problem came back again. I'm not sure if it's the whole thing or a track-to-track issue. That's something we need to find out.

If it's a voltage mis-match, metering error, etc., I'd be curious of your findings as well.

[Brain]

Originally Posted by soupking

I've been having similar issues with my JH24. We got out an oscilliscope and re-caled the master bias oscillator. That seemed to work. Then we re-biased/High-EQ'd it and the problem came back again. I'm not sure if it's the whole thing or a track-to-track issue. That's something we need to find out.

If it's a voltage mis-match, metering error, etc., I'd be curious of your findings as well.

After you have adjusted the master bias oscillator on the JH-24 you may have to adjust the bias board coil (on each of the 24 cards) for max output. You will need a coil alignment tool (plastic are affordable at decent parts store). The procedure is clearly defined in the manual.

Later,
Brain

[Brad McGowan]

I think the JH110 may be a little different from the JH24 in this department, but I'm curious to hear what happens with your deck.

Damn vintage gear...why does it have to sound so good, but work so crappily? If only Otari sounded good....

Brad

[soupking]

Originally Posted by Brad McGowan

I think the JH110 may be a little different from the JH24 in this department, but I'm curious to hear what happens with your deck.

Damn vintage gear...why does it have to sound so good, but work so crappily? If only Otari sounded good....

Brad

Yeah, really.

What Brain said above might be very on the level because we checked it out on a few channels and it was quiet as could be. However, after calibrating the thing, the channels we test recorded/erased on could have been completely different and the "silver boobs" (as I call them cuz I'm an idiot) might need tweeking.

You might actually have something similar in terms of issue with your bias/erase cards as well, but I'm not a tech, so don't quote me on that.

Thanks Brain!

[Brain]

I believe that the 110s had a similar adjustment.
I don't remember exactly, but I think those white squares
with the metal screws are something similar to the
Bias coils on the JH-24. Check the manual

Later,
Brain

[amorris]

the white squres i.e. variable capacitors are for the bias trap. low pass filter on repro/sync to remove bias reproduction causing artifacts in the audible range. the bias peak circuit on any tape machine will be the tunable coil described earlier.

erase is about 240k and bias about 140khz. ? a Fluke might be attenuating your results if it doesnt see 240 well. Scope it.

also at the factory we would record 1k +10 to hit it good and hard then dial erase for >70db of erase. (-60 then add the +10 signal) this would put it in the dirt as they say.

head height, azimuth and zenith are just as critical as wrap. this is why full alignments are done only with ALL the gear at THE SAME TIME (head blocks). youve got to finish what you start.

[Brad McGowan]

On the JH110 there are large white trimmer caps on each audio motherboard. The middle one adjusts erase peak. The bias oscillator frequency is adjusted by the tuned coil on the strip board at the back of the topmost drawer. There is also a trimpot there that affects voltage level.

Both the erase and bias are 120kHz on the JH110.

I think you are probably right about finishing what I started. I've been assuming that my erase head is properly adjusted since I just had a relap and optical alignment, but perhaps that's those are the adjustments I really need to make to dial it in correctly.

thanks,
Brad

[amorris]

Both the erase and bias are 120kHz on the JH110.

my bad, boy its been a long time since I've actually been that deep on a 110.

I would think that an optical align would get you pretty darn close....

[Brad McGowan]

Originally Posted by amorris

my bad, boy its been a long time since I've actually been that deep on a 110.

I would think that an optical align would get you pretty darn close....

That's what I would think. But on my last attempt at adjusting the erasure I was only hitting about -60dB on the erase. That hardly seems good enough if I want to reuse tape. I did have to adjust the azimuth on the repro head when I got the headstack back from JRF. So maybe it's not too unreasonable to have to tweak the erase as well. We'll see. Just waiting for the oscilloscope to show up.

Brad

[amorris]

-60 isnt too far off. -72 was a typical good result at the factory. so you're looking for about 10db more. but if you are maxing out the voltage (40v not 50 as in the book), it would seem something is loading that voltage. I thought I would read in the 70volt range on the rec head itself. (bias). again its been a very long time since I measured at the head.

you should get a de-gausser. the table top models that will erase you credit cards. they will clean a tape close to virgin. I would de-gauss and run "virgin" for the actual master run. (not that same day but I would go through and do all the scraps and use em when I need them)I think it makes a difference.

[Brad McGowan]

Those are quite expensive from what seen.

Verity V94 Table Top Bulk Eraser

Are there cheaper models available? If buying used what would be appropriate for 1" tape?

thanks,
Brad

[alkooloid]

I was hoping my 110c was just erasing a narrower path than
some other machines I had and that it was
edge bleed.

Sounds great, but no techs around here, and I'm scared to
dive in. How'd the bulk erase thing work out?
May be one in my future!

[Brad McGowan]

I've been making some progress on the erase issue. Having the oscilloscope has definitely helped. And using the hum shield too. Duh.

Now I seem to have developed a rather annoying problem. If I rewind tape such that it spools off the take-up reel, neither motor stops, but instead the reel of tape spins faster and faster and won't slow down unless I turn off the machine. I know that's not normal. I also noticed that if there is no tape on the machine and I power it up that both reels will spin. Is this normal?

What might cause this runaway motor problem? Where should I troublshoot first? Is it an optical sensor issue?

thanks,
Brad

[Brain]

Originally Posted by Brad McGowan

I've been making some progress on the erase issue. Having the oscilloscope has definitely helped. And using the hum shield too. Duh.

Now I seem to have developed a rather annoying problem. If I rewind tape such that it spools off the take-up reel, neither motor stops, but instead the reel of tape spins faster and faster and won't slow down unless I turn off the machine. I know that's not normal. I also noticed that if there is no tape on the machine and I power it up that both reels will spin. Is this normal?

What might cause this runaway motor problem? Where should I troublshoot first? Is it an optical sensor issue?

thanks,
Brad

It sounds like you have multiple issues.

The reels turning when no tape is on the machine sounds like the optical sensor that tells the machine that tape has been threaded onto the machine needs adjusting. There is a trim pot under the deck lid. adjust this until the motors stop turning.

The other issue could be that the contacts are corroded for the phase lock loop and the analog torque board where they connect to the mother board. remove and reseat the boards. Then you will need to go through the transport alignment. Also if the boards still have the old tall Red chip sockets, these can cause stability problems. I replaced these years ago and received much better transport stability.

It also never hurts to make sure the contacts on the cables from the power supply to the mother board are clean as well. Dirty contacts will be your constant and never ending friend/enemy with these machines.

Later,
Brain

[Brad McGowan]

Thanks for the tips. The weird thing is that this new runaway motor issue just popped up a couple days ago.

Thankfully all the red sockets have been replaced on all PCB's. I'll be sure to check the optical sensor. Perhaps there's something blocking it or a lousy connection. I'll check the power connectors as well.

Can you briefly explain why I would have to redo my alignment if I just reseat the phase lock loop and analog torque boards?

thanks,
Brad

[soupking]

Hey Brad,

I don't know if this is a dead issue, but we figured out what the problem was with the tracks not erasing properly on the JH24.

We had to calibrate the bias/erase coils on the bias cards. A couple of them still won't cooperate. Due to the age, my tech says it's probably a re-capping issue.

However, we got most of the channels to erase pretty darn well, some to dead calm. Some better than others, but it's an old machine.

We still want to go back and peak the bias and erase master, but our pic was giving us trouble. For some reason the cal pick was to small for the hex nuts in the coils tubes. ?? Go figure. I wrapped a layer of masking tape around it and now the pic works fine.

If you run into that problem again, it could be a simple calibration problem. Maybe not, but that's what we ran into.

[Brad McGowan]

Maybe I should just recap my bias cards. I've done all the others but the bias cards. It wouldn't hurt.

Currently I think I have all of the channels but one erasing properly. Erase head wrap adjustment was the key. Also I turned up the bias level just short of clipping the waveform for all the channels. Well except for track 2 which is being a pain. I also found that using the hum shield greatly improved the hum issue I was having. I feel like a complete idiot on that one.

Oh how I love to solder...

Brad

[Brain]

Originally Posted by Brad McGowan

Can you briefly explain why I would have to redo my alignment if I just reseat the phase lock loop and analog torque boards?

thanks,
Brad

The quality of the connection to the mother board is critical to the stability of the cards functionality. Over time if a card has been in a particular spot (referencing the cards socket to the pins on the mother board) then corrosion can pit the metal at that spot. This is when Stability can be an issue. If you hit that exact spot on the pins again when you re-insert your cards, you will have a different reaction to voltages and control signals than if you found a clean up-pitted portion of the mother board pins. I have a machine that has lost ALL of the metal coating on the pins and the underlying metal oxidizes 10 times faster than it might normally. This machine has MAJOR reliability issues.

So when you reinsert your phase lock loop and analog torque boards the voltages/resistance that the cards see and react to may be different from what you had before. Your "DC offet null", "Idle" and "Tension" settings will not be at their optimal best. You will be greatly served by redoing these settings. It only takes 5 minutes (as long as the machine cooperates). There can be cases where you put the analog torque board on and how it reacts will not allow you to get an accurate setting on the "DC offset Null". In this case you will need to re-seat the card again and then realign your card again. The older tha machine, the condition of the mother board pins and cards molexes, red IC sockets, all seriously affect the performance of your transport.

Also

Originally Posted by soupking

I don't know if this is a dead issue, but we figured out what the problem was with the tracks not erasing properly on the JH24.

We had to calibrate the bias/erase coils on the bias cards. A couple of them still won't cooperate. Due to the age, my tech says it's probably a re-capping issue.

On the Multitracks, If you recap them, you will need to Re-do ALL of the coil adjustments, as well as any other bias related settings. They WILL be affected by a re-cap.

Later Guys,
Brain

[soundbarnfool]

I find that once you get the beast up and running 9 times out of 10 it's a connection/seating issue... So, re-seat, reconnect, clean contacts.