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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 13th Jun 2018, 7:48 pm   #1
Barks67
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Default Fostex E16 - any experienced here?

Hi all

I have just picked up an old Fostex E16 and have been gradually waking it up.
Mechanically it is all very sound though it does look like a relap needed as track one weak, especially in the treble.
The other tracks play fine in isolation.

To my question...

I have a Webber test tone tape that came with it and I am experiencing some weirdness on playback which I will try to explain here.

When all tracks (16) are playing back there is a weird "Dalek like' oscillation/distortion to the tone introduction voice overs and the tones when they play, clearly oscillating.

BUT

If I put all tracks into record mode AND have the record button pressed to record ready - then play the tape - any selected track that is dropped out of input monitor plays back absolutely fine.

More than two and the oscillation starts to come back.

I notice than in isolation the meters are all showing 0dB as they should but when ALL playback the levels fluctuate up and down either side of 0dB.

Its almost as if the line out bus from the cards cannot cope - but this does not make sense as it is passive all the way to the RCA outs.

I wondered maybe if this is a power supply issue and the boards are not getting a smooth supply?

Any help appreciated. I have the full service manual.

Barks
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Old 15th Jun 2018, 6:55 pm   #2
jamesperrett
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Default Re: Fostex E16 - any experienced here?

I have an E16 and an E8 but haven't experienced the problem that you mention.

What happens when you feed a tone into the inputs - do they also warble? You only need to connect the first 8 as these are automatically patched through to the upper 8 when nothing is connected to the respective inputs.

It certainly could be power related. I suspect that the meter LED's may take more current than the audio circuits when all the segments are lit so it might be worth checking to see if the problem is related to the number of segments alight.

Edit to add: The edge tracks are very susceptible to any dirt in the tape path and, due to the head design, if your tape is slightly wider than the tapes normally used with the machine you may find the head to tape contact isn't as good as it should be.
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Old 17th Jun 2018, 12:16 am   #3
Barks67
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Default Re: Fostex E16 - any experienced here?

Thanks James for your reply.

I finally got to run signals through the machine today and can discount the tape head for this issue - even though track one is weak.

With no tape on the machine and the inputs receiving signals (all directly monitored to the outputs) the same distortion appears.

It clears up gradually as you disengage inputs from monitor - so it must be something to do with the replay cards and the output side, as the fault is replicated when any tape is played.

I can only think at this stage that as the head has worn and signals got weaker as a result, somebody has maybe cranked the outputs on the cards and this may be causing this?

I have kept signals coming in on a loop from Protools and prodded every connector (with a very long chopstick!) looking to see if there is possibly a dry joint, but to no avail.

It may be that I need to get the head checked anyway and relapped and aligned so that at least some proper calibration can be made.

onwards...
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Old 17th Jun 2018, 11:45 am   #4
Ted Kendall
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Default Re: Fostex E16 - any experienced here?

You could do worse than inspect a channel card for signs of deteriorating electrolytics - the G24 in particular has form on this...
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Old 17th Jun 2018, 2:36 pm   #5
jamesperrett
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Default Re: Fostex E16 - any experienced here?

I haven't had any problems with electrolytics on my machines but then they've been in reasonably regular use (switched on at least once every couple of months) for their whole lives.

However, if it is a fault with a channel card it might be worth removing them one at a time to see if the fault goes away when a particular card is removed. Always switch the machine off when removing or replacing these cards.

However, before you remove anything I'd check the power supply voltages on the backplane with a voltmeter.

Quote:
Originally Posted by Barks67 View Post
I can only think at this stage that as the head has worn and signals got weaker as a result, somebody has maybe cranked the outputs on the cards and this may be causing this?
That's very unlikely - normal signals don't really get weaker with head wear although high frequencies may reduce and head to tape contact is worse.
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Old 17th Jun 2018, 3:24 pm   #6
TIMTAPE
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Default Re: Fostex E16 - any experienced here?

I agree with James that this looks like a power supply issue. Probably a weak power supply which would explain the pulsing (hum?) in the repro stages when it drops out of regulation. I'd be checking that the relevent regulated voltages are within tolerances at all times.

Also as James said, wear in repro heads doesnt normally cause a gradual drop off in output. Most of the head's output remains essentially constant throughout the life of the head but excepting for mechanical tape to head contact issues, the playback high frequency response actually improves with head wear right up to the point where the head gap opens and fails. Then there is a sharp drop off in response and the head has no more useful life.

Last edited by TIMTAPE; 17th Jun 2018 at 3:33 pm.
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Old 17th Jun 2018, 8:05 pm   #7
Barks67
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Default Re: Fostex E16 - any experienced here?

Thanks for all the replies everybody.

This machine has been in storage and not used for the last 10 years.
The issue of off spec electrolytic caps is a possibility as a result of this.
It used to belong to Steve Wright of Grange Hill, Brookside and Holly Oaks fame.

I think it must be a power issue. The connector board for all the record/replay boards should be +18v according to the service manual schematic so I'll start there - recapping the power supply may be the first step.

I tried again bringing in signals very low peaking about -7dB and it 'kind of' behaved better.

Quote:
Originally Posted by jamesperrett View Post
That's very unlikely - normal signals don't really get weaker with head wear although high frequencies may reduce and head to tape contact is worse.
Good point - thanks

Quote:
Originally Posted by TIMTAPE View Post
I agree with James that this looks like a power supply issue. Probably a weak power supply which would explain the pulsing (hum?) in the repro stages when it drops out of regulation. I'd be checking that the relevent regulated voltages are within tolerances at all times.

Also as James said, wear in repro heads doesn't normally cause a gradual drop off in output. Most of the head's output remains essentially constant throughout the life of the head but excepting for mechanical tape to head contact issues, the playback high frequency response actually improves with head wear right up to the point where the head gap opens and fails. Then there is a sharp drop off in response and the head has no more useful life.
Thanks Tim
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Old 19th Jun 2018, 9:37 pm   #8
jamesperrett
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Default Re: Fostex E16 - any experienced here?

Quote:
recapping the power supply may be the first step.
I wouldn't necessarily go recapping anything until you've found the real problem. A few minutes spent checking voltages would be very worthwhile.
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Old 20th Jun 2018, 12:58 am   #9
Barks67
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Default Re: Fostex E16 - any experienced here?

Thanks.

I'm taking it to the main Multitrack specialist in Yorkshire tomorrow for assessment. I'll report back.

Barks
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Old 23rd Jun 2018, 2:21 pm   #10
Barks67
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Default Re: Fostex E16 - any experienced here?

First update:

Engineer rang yesterday and initial assessment is that previous owner has ramped up ALL the outputs on the cards.
The whole shebang is massively out of whack - so first step is to try an recalibrate to spec. Also possible there is power supply ripple that needs taming.

ugh.
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Old 23rd Jun 2018, 8:51 pm   #11
jamesperrett
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Default Re: Fostex E16 - any experienced here?

Quote:
Engineer rang yesterday and initial assessment is that previous owner has ramped up ALL the outputs on the cards.
Sounds like they were trying to use it with a mixing desk designed for +4dBu levels. That's a pretty simple job to correct - probably a 10 minute job if you have the right setup. The ripple on the power supply sounds like the real issue here.
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Old 23rd Jun 2018, 11:25 pm   #12
Barks67
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Default Re: Fostex E16 - any experienced here?

I'm not sure if that is the case here as it was originally partnered to this Soundtracs PC Midi which can do both -10 and +4. I bought the console 8 years ago and the Fostex has not been used for 10 years.
Maybe they were trying to get more "analogue distortion"...
I'll know more next week, but yes ripple is interesting and may be of use to others who have these if it is an emerging issue.
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Old 24th Jun 2018, 12:53 pm   #13
Barks67
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Default Re: Fostex E16 - any experienced here?

Btw, here is a pic of the head.
You can see why track one is an issue though it looks like wear is consistent on the others.
Getting it assessed will be the next step - most likely to Summertone.
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Old 24th Jun 2018, 1:09 pm   #14
Barks67
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Default Re: Fostex E16 - any experienced here?

Another view which shows the ares of no wear - either side of the bright reflection of the head contact area.
Not sure if there is enough meat on this for a relap - though I cannot discern any gap opening?
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Old 24th Jun 2018, 1:15 pm   #15
Ted Kendall
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Default Re: Fostex E16 - any experienced here?

+1 for Terry - he's been making and reconditioning heads for ever. Looks to me as if it will take a lap...
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Old 25th Jun 2018, 12:19 am   #16
TIMTAPE
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Default Re: Fostex E16 - any experienced here?

Quote:
Originally Posted by Barks67 View Post
Another view which shows the ares of no wear - either side of the bright reflection of the head contact area.
Not sure if there is enough meat on this for a relap - though I cannot discern any gap opening?
It's certainly had some work and there is some keystoning. I think it's JRF Magnetics in the US who will not charge if in the relapping process the gap opens up. I dont know if this is common or not.

As heads wear the metal away, their inductance lowers and that inductance reading can be used an a guide to remaining head life but only if the technician knows at what inductance the gaps in the pole pieces open up.

The lifespan after relapping depends on how the head is relapped. One can relap conservatively to remove the ridges at top and bottom ( adjacent to tracks 1 and 16 here) and to partially restore some radius. This can be done (carefully) by hand and without expensive equipment.

The other way fully restores the radius to original specs. Unfortunately this will lead to faster head wear and a more shortened life.

We chooses our poisons.

Tim
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Old 25th Jun 2018, 8:08 am   #17
Barks67
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Default Re: Fostex E16 - any experienced here?

Thanks Tim , very useful info.
Not sure if this has had any work as the adjustment screws are still sealed with wax and have not been disturbed.
The tech suggested at this point to maybe leave it as a 15 track. If removed and head lap deemed not possible, it'll be very difficult to reinstall and get back any current performance it currently has. Once track 2 goes off then consider options.
You do indeed choose your poison!
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Old 25th Jun 2018, 10:48 am   #18
TIMTAPE
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Default Re: Fostex E16 - any experienced here?

What I meant by "had some work" was that the head looks worn, not that it's been relapped.

Tim
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Old 25th Jun 2018, 11:01 am   #19
Barks67
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Default Re: Fostex E16 - any experienced here?

Understand thanks.
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Old 12th Jul 2018, 1:50 pm   #20
Barks67
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Default Re: Fostex E16 - any experienced here?

Ok, Fostex is coming back to life.
All problems are down to two voltage regulators being completely out of spec. These are the ones that are strapped to the big heat sink at the top of the machine.
Being calibrated now. Track one is weak but 2 to 16 are in good shape. Down to poor calibration at manufacture. The tech may have some Fostex heads that can be assessed for relap. He used to work on these for KGM and they'd just remove and replace with new and not bother with relapping. May have a good one.
Thanks for all your help.
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