Listen, I know my trade well, been in it for decades now in a professional way.
But this bastard of a tape deck is driving me nuts.
I've been over the whole unit, replaced those "fuzzy" caps, did scope readings, voltages, signal quality, the works.
Playback board gone over and calibrated, compared channels, no problems.
Sent the head block out to JRF, it was checked over, alignment, inductive balances, etc..... YET....... there's STILL a problem with the RIGHT CHANNEL PLAYBACK LEVEL ON THE TWO-TRACK PLAYBACK HEAD!
Must be over -10dB difference compared to the left channel.
Four track head plays great- perfect balance both channels.
JRF claims they didn't have any issue when this head block was installed on their RS-1500.
They state the heads have about 80 percent life left in them, no need to relap or replace.
I don't understand how that could be.
WHY the droop in level on the R channel playback head?
The tape's riding perfectly right down the middle of each head!...wear pattern agrees!
In ALL my decades of servicing other people's "broken junk", this has GOT to be one big bastard job.
Who's got an answer or solution?
But this bastard of a tape deck is driving me nuts.
I've been over the whole unit, replaced those "fuzzy" caps, did scope readings, voltages, signal quality, the works.
Playback board gone over and calibrated, compared channels, no problems.
Sent the head block out to JRF, it was checked over, alignment, inductive balances, etc..... YET....... there's STILL a problem with the RIGHT CHANNEL PLAYBACK LEVEL ON THE TWO-TRACK PLAYBACK HEAD!
Must be over -10dB difference compared to the left channel.
Four track head plays great- perfect balance both channels.
JRF claims they didn't have any issue when this head block was installed on their RS-1500.
They state the heads have about 80 percent life left in them, no need to relap or replace.
I don't understand how that could be.
WHY the droop in level on the R channel playback head?
The tape's riding perfectly right down the middle of each head!...wear pattern agrees!
In ALL my decades of servicing other people's "broken junk", this has GOT to be one big bastard job.
Who's got an answer or solution?
Is the switch on the head block like the Otari MX-5050 with 2 and 4 track replay heads or somewhere else?
I had a similar problem with one of my MX-50s, but it became clear to me that someone had been twiddling some head adjustments...
Finally is it just low but otherwise OK or do you observe major fluctuations in level with 10kHz test tape?
Tape tension correct?
I'm out of ideas.. 😀 Please let me know what you find
I had a similar problem with one of my MX-50s, but it became clear to me that someone had been twiddling some head adjustments...
Finally is it just low but otherwise OK or do you observe major fluctuations in level with 10kHz test tape?
Tape tension correct?
I'm out of ideas.. 😀 Please let me know what you find
Kevin, to add to what I already mentioned in post #1....
The slide switch on the headblock is a simple 2PDT type, It's been cleaned, tested for operation. All it does is switch the "hot side" of either the 2T or 4T playback heads.
I've checked the cables from headblock connector to the input amp.
Cables are perfect - no shorts, nothing wrong. - Head reads 149 ohms for each channel.
Mind you, I had to pull the massive capstan motor/flywheel out to access the block connector plate.
I told John (JRF) while he had the block, that I eliminated all possible reasons for the R/ch 2T play head level drop.
We discussed replacement, relapping, but he advised me that the original head was fine.
I'm not so sure.
I even confirmed it by reversing the head connector at the board input - and the low level and normal level SWITCHED sides - just as I predicted.
So it's THE PLAYBACK HEAD - it HAS to be.
It's certainly not the playback amp (which also has been recapped/aligned/etc)
How can I finish calibrating the unit - for recording levels, etc, if I can't rely on the 2Track head?
The right channel volume is low by about 10db and steady, with no fluctuations or drop-outs.
No distortion, but perhaps a bit weak in the highs, not sure.
And there's no way this can be compensated for by the internal gain adjustments.
It's just not right.
Tape tension is perfect - The initial work on this machine was my thorough overhaul of the mechanicals, brakes, tape lifters, pinch roll tension, lubed, etc etc.
Machine runs flawlessly through all modes.
Adding tension to the tape makes no difference.
The slide switch on the headblock is a simple 2PDT type, It's been cleaned, tested for operation. All it does is switch the "hot side" of either the 2T or 4T playback heads.
I've checked the cables from headblock connector to the input amp.
Cables are perfect - no shorts, nothing wrong. - Head reads 149 ohms for each channel.
Mind you, I had to pull the massive capstan motor/flywheel out to access the block connector plate.
I told John (JRF) while he had the block, that I eliminated all possible reasons for the R/ch 2T play head level drop.
We discussed replacement, relapping, but he advised me that the original head was fine.
I'm not so sure.
I even confirmed it by reversing the head connector at the board input - and the low level and normal level SWITCHED sides - just as I predicted.
So it's THE PLAYBACK HEAD - it HAS to be.
It's certainly not the playback amp (which also has been recapped/aligned/etc)
How can I finish calibrating the unit - for recording levels, etc, if I can't rely on the 2Track head?
The right channel volume is low by about 10db and steady, with no fluctuations or drop-outs.
No distortion, but perhaps a bit weak in the highs, not sure.
And there's no way this can be compensated for by the internal gain adjustments.
It's just not right.
Tape tension is perfect - The initial work on this machine was my thorough overhaul of the mechanicals, brakes, tape lifters, pinch roll tension, lubed, etc etc.
Machine runs flawlessly through all modes.
Adding tension to the tape makes no difference.
Hmm, that does sound like a head problem to me... My only other suggestion would be to swap the head connections right at the head and see what happens. I expect it will not change the outcome.
I've only had one set of heads done by JRF but was ecstatic with the results, and I know a number of other people who use JRF and have had similarly positive experiences.
I assume you were using a test tape, and behavior observed is also the same when doing a test recording..
I've only had one set of heads done by JRF but was ecstatic with the results, and I know a number of other people who use JRF and have had similarly positive experiences.
I assume you were using a test tape, and behavior observed is also the same when doing a test recording..
I've got several test tapes, and some made by myself on certified machines using Maxell UDXL.
Playing a 1/4 track tape sounds perfect, then switching it to the 2 track head - bam!.... right channel drops way off, left side is only a tad lower.
According to JRF, the paperwork says it's only a 1.5dB difference in tracking.
?????
Playing a 1/4 track tape sounds perfect, then switching it to the 2 track head - bam!.... right channel drops way off, left side is only a tad lower.
According to JRF, the paperwork says it's only a 1.5dB difference in tracking.
?????
Definitely an odd one, swapping the leads at the head should be definitive - if it swaps to the other channel it's got to be the head, if it doesn't it's got to be something between the head and the switch - doesn't really make sense, but something ruled out is generally helpful.
I've been living in my own little h*ll as you know, tape recorders are challenging.
My experience has been mostly obvious only in retrospect.. LOL
I am assuming this is the same behavior observed before the head stack went out...
Shoot me a PM about the head when you have a moment.
I've been living in my own little h*ll as you know, tape recorders are challenging.
My experience has been mostly obvious only in retrospect.. LOL
I am assuming this is the same behavior observed before the head stack went out...
Shoot me a PM about the head when you have a moment.
Foo on tape. Make a flux loop. An insulated wire against the head gaps, parallel to gap. Center it as well you can by eye; it matters but not too much. Wire to a signal generator with a series resistor to keep the siggen happy. Put in Play, bring up level slow until you have a reading. Note L and R. Sweep frequency and look for lumps/slumps.
It is not absolutely sure to be throwing the same flux on both gaps. But with casual care it should be within a dB. You can check that by moving the wire across the head, or look for separate maximums on L and R.
I have not done this since Nixon left office, and do not recall if a sweep should real flat or 6dB/oct or what. I know you are smart enough to take it from here.
Is there ANY chance your head has been mixed-up with someone else's?
EDIT: M A N Q U E N . N E T - A U D I O is the technique though he calls for many feet of wire and I remember "one turn".
EDIT EDIT: Some guy named AMPEX 🙄 : THE USE OF FLUX LOOPS FOR CALIBRATION OF MAGNETIC REPRODUCERS BY. Alastair M. Heaslett Ampex Corporation - PDF Free Download Download button below reader window. Leads to http://docplayer.net/storage/77/75459660/1603070044/hvCeaZQcB1d-i1TZXBYW3w/75459660.pdf but probably won't work direct.
It is not absolutely sure to be throwing the same flux on both gaps. But with casual care it should be within a dB. You can check that by moving the wire across the head, or look for separate maximums on L and R.
I have not done this since Nixon left office, and do not recall if a sweep should real flat or 6dB/oct or what. I know you are smart enough to take it from here.
Is there ANY chance your head has been mixed-up with someone else's?
EDIT: M A N Q U E N . N E T - A U D I O is the technique though he calls for many feet of wire and I remember "one turn".
EDIT EDIT: Some guy named AMPEX 🙄 : THE USE OF FLUX LOOPS FOR CALIBRATION OF MAGNETIC REPRODUCERS BY. Alastair M. Heaslett Ampex Corporation - PDF Free Download Download button below reader window. Leads to http://docplayer.net/storage/77/75459660/1603070044/hvCeaZQcB1d-i1TZXBYW3w/75459660.pdf but probably won't work direct.
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Spend another 3 1/2 hours today on that damned machine.
Disassembled/cleaned 2/4 switch, previously just cleaned and lubed, this time scrubbed the contacts with TarnX then CRC.
Of course, no change, head wiring all good.
Service manual has a misprint at the 2/4 switch, along with a .01uf wired wrong.
In play, if a jumper is used across the +L/+R connector from the heads, the resulting mono signal is balanced - so it's not anything with the playback amp.
There is no leakage (resistance) anywhere along the chain from heads to amp connector.
All voltages of the play amp are well within spec on the print.
Its GOTTA be the HEAD!
Yet...... everything checks out.
I've got a funny suspicion that the 2 track play head is going to be replaced.
I've got an MX-5050 sitting around for a couple of years - I might just swap out the head myself.
Then see what's gonna happen.
Disassembled/cleaned 2/4 switch, previously just cleaned and lubed, this time scrubbed the contacts with TarnX then CRC.
Of course, no change, head wiring all good.
Service manual has a misprint at the 2/4 switch, along with a .01uf wired wrong.
In play, if a jumper is used across the +L/+R connector from the heads, the resulting mono signal is balanced - so it's not anything with the playback amp.
There is no leakage (resistance) anywhere along the chain from heads to amp connector.
All voltages of the play amp are well within spec on the print.
Its GOTTA be the HEAD!
Yet...... everything checks out.
I've got a funny suspicion that the 2 track play head is going to be replaced.
I've got an MX-5050 sitting around for a couple of years - I might just swap out the head myself.
Then see what's gonna happen.