Tascam 238

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ruffrecords

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Nov 10, 2006
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Location
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I have a Tascam 238 8 track cassette recorder which in many ways works fine once it has warmed up. However, when switched on from cold, the capstan runs about 10% slow and it is very noisy. There is also a noticeable drop in the frequency of the noise as when you engage play. After sitting there for an hour the noise disappears and the capstan speed is with 2% of nominal. I suspect this is a mechanical problem rather than the classic motor servo needs a recap problem. Maybe some sticky when cold lubricant.

Any suggestions?

Cheers
 
Yes, sticky lubricant would be my guess too.
I have an older pedestal fan that has the same problem, runs very slowly when first switched on, and then gets up to normal speed after about 5 minutes.
 
I would drop the capstan from its bearing. Clean it thoroughly with IPA, using a cotton bud and lubricate it with Singer Sewing Machine oil.
That oil does not dry and becomes thinner when warm to lubricate more thoroughly.
Use sparingly.
All oils attract dust so fit the dust cover after lubrication.
 
I would drop the capstan from its bearing. Clean it thoroughly with IPA, using a cotton bud and lubricate it with Singer Sewing Machine oil.
That oil does not dry and becomes thinner when warm to lubricate more thoroughly.
Use sparingly.
All oils attract dust so fit the dust cover after lubrication.
I will do that and report back. I don't have any sewing machine oil but I have shaver oil - will that do?

Cheers

Ian
 
I will do that and report back. I don't have any sewing machine oil but I have shaver oil - will that do?

Cheers

Ian
The shaver oil is very fine and similar to sewing machine oil.
PTFE (GT85) I have no experience with, except to lubricate the front forks of mountain bikes.
 
PTFE is essentially nanoplastic, made from fluorinated hydrocarbons. The particles are not only toxic, but also never breaks down (PFAS). Your nonstick pan gives off tiny particles of it into your food.

Very slippery but not good in sintered bronze bearings, these are made to be lubricated only with oil.
 
The shaver oil is very fine and similar to sewing machine oil.
PTFE (GT85) I have no experience with, except to lubricate the front forks of mountain bikes.
PTFE is also known as teflon, so maybe don't drink it.

I vaguely recall teflon jacketed wire back in the 60s, used for high temperature applications.

JR
 
Used a lot in UK for military electronics. Great stuff - does not shrink when soldered like PVC does.

Cheers

ian
Yup I was introduced to teflon insulated wire working on a Navy (Deep Submergence Rescue Vehicle) project, while working at MIT Instrumentation Lab back in the 60s. As I recall we had a hot wire stripper (two red hot wires) to strip off the teflon insulation neatly.

Modern thermal strippers apparently use different technology but this was over half a century ago.

JR
 
A relatively unknown wire insulation is "irradiated PVC". Higher melting point than ordinary PVC, yet cheaper and easier to strip compared to Teflon. I was introduced to it when I went to "Crown Amplifier school" at the factory back in the 1970's.

Bri
 
It seems the Tascam 238 problem is worse than I thought. I dubbed a tape across to a couple of tracks of the 238. At the beginning of the tape the flutter was terrible but after a couple of minutes it seemed to settle down. So I dubbed up to the middle of the tape hoping it would be even better, but on playback, in the middle it would occasionally slow way down for a few seconds and then recover. So I suspect something other than just lubrication is wrong.

Cheers

Ian
 
I definately second the Singer light machine oil for ball bearings where the lube has dried out .
Its unlikely to cause any compatibillity issues with the grease left inside the bearing either,
Small cassette type capstans dont tend to have a ball bearing but usually a sintered bronze bushing (possibly self lubricating) ,
Im not sure what the appropriate way to deal with them is , using a spray oil product isnt a good idea in a tape deck , you could try dropping a tiny amount of light oil right where its needed with a pin .
Again Im not sure of the exact detail of the tape mech used in that machine , you could have a drive belt issue going on , in a few other rare cases I found tape deck motors themselves were defective , there was no outward signs of any damage and they might appear to be working fine for a while but then for no apparent reason it would go off on a wander speedwise . One other thing probably worth checking is the preset pot that sets the speed .
You might also have a layer of oxide built up on the pinch roller which is causing the tape to slip sometimes , cotton buds dipped in iso should remove all that easily ,although it might require several goes at it to get it properly clean if theres a heavy build up . Examine the capstan and pinch roller for hairs or other debris caught up and wound around it . Also bear in mind some parts have plastic bearing surfaces , like the pinch wheel , you dont want to put anything petroleum based there , silicone based grease is the usual thing used as far as I remember .
Working on the mechanisms of these logic controlled transports isnt all that easy , you may have luck finding a youtube tutorial to help you .
 
The cintered brass bearing is known as an Oilite bearing because oil applied to it soaked into the tiny holes in the brass, a bit like a sponge and as the bearing warms up, it releases more lubricant which in turn cools the bearing.
Singer Sewing Machine light oil is particularly useful in this employment.
 
Used a lot in UK for military electronics. Great stuff - does not shrink when soldered like PVC does.

Cheers

ian

Also good insulation properties so used in various high voltage ' low leakage applications eg cable jackets and low leakage component stand offs.
Can be resistant to 'normal' wire strippers. Best way is to 'score and bend' if not using thermal strippers.
Teflon is proprietary name for PTFE developed/manufactured out of DuPont spin off.
 
I took the mechanism out of the enclosure last night and inspected it. One electrolytic cap had fallen off and so had the 9V zener that provides the supply to one of the chips. Ordered some caps and zeners so I can replace most of them.

Cheers

Ian
 
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