Tascam 38

[evm1024]

I picked up my first tascam 38 today. Comes with 2 reels of 456 (90 and 95 date codes) and a snake. $75....

Of course the capstan does not turn - perhaps a belt, but I don't hear the motor. And the playback head had wear. But the record head is in nice shape. All but 2 of the meter lamps are out.

Now all I really need is some time - and a take up reel, and a manual with a schematic (actually my 34 manual should cover most of this more or less).

It looks like it could be a nice deck. You can see where it has been serviced and kept clean. THe lifters and some guides have been rotated.

It appears that I get to the belt from the front. Is this correct?

Not sure what I'll do with. Perhaps a choir.

 

[SteveM]

Good deal EVM. Hope you get it working. I'm actually getting ready to send my heads to get relapped. Then I need to put them back on and figure out how to get them back to spec. Yes, the belt is from the front panel. It's a little tricky to get at because it runs under the headstack. Good luck.

 

[Beck]

Congrats Ethan.

Sounds like it could be the capstan drive belt. Yes, you get to it by removing the front panel. You should still hear the capstan motor when lifting the right tension arm... I think. At least that's how it goes on the TSR-8. With some machines the capstan spins continuously. I haven't used a 38 for so long I can't remember for sure. Either way the motor should spin when you turn the machine on or when you lift the tension arm.

Could also be the switch that engages when you lift the tension arm... no big deal to fix.

Hey, make sure to toss the 456 from 1990… well you can keep the reel for a spare.

As long as you have a good record/sync head you’ll be fine. Those heads are the same part number. Unlike some older designs, playback from the sync (record) head on the TASCAM is just as Hi-Fi as playback from the repro head.

 

[evm1024]

Thanks guys

I'm just back home from an Avalanche recert class and doubt that I'll get up the energy to take it apart tonight.

I need a take up reel so I'll mostlikely convert one of my 1/4" over to 1/2". So far that tape does not look sticky using the kimwipe swipe test.

Anybody got a pdf of the service manual? ( I collect them you know...)

No motor sound is a worry to me. I should hear something. But then again it could be a disconnected cable or a bad drive transistor.

More later.

 

[Dr ZEE]

cool!

Sounds like a project.
Good luck, and by that, I suppose, I mean - less fun with the project

No motor sound is a worry to me. I should hear something. But then again it could be a disconnected cable or a bad drive transistor.
.

so did you move the arm yet?

post updates.

 

[evm1024]

Some looking at it today....

OK, As the saga continues....

Pulled the arm up some time ago. No sound of the capstan motor. The belt looks and feels good. The capstan, flyweel,motor all turn by hand OK.

Pull the capstan servo board. Voltages look OK. Speed select OK (say did you know that the 38 could 7.5 ips? I think that you could make it do 30 ips) Pitch control OK. tension switch does change the control voltage. One motor lead 32V(+-) the other near ground. OK.

Put a scope on the feelback from the motor and rotated the shaft. Looks OK I see a sine wave from the motors tach.

I see that the drive transistor has been replaced as well as the outputs drive transistor.

Did a quick look for the control IC (a JRC 2901n) thinking that it would be a PLL IC but find out that it is a quad comparator. Looks like they implemented the servo this way (one of the comparators as an osc and the other to modulate the drive voltage.)

Using a 34B manual for some of this. No diagram of the motor control in either my 34B or 32 manual. Drats, I may have to diagram out the capstan motor board.

So right at the moment I've got 32 volts going to the motor on one leg and 0 on the other. The motor is not spinning so that makes me think that the motor is bad. (got an open in a winding somewhere. assuming brushless)

I'll have to look a little more at it and come up with a test or 2.

Ah, Looks like the A-3440 uses the same servo circuit. I got the schematic from there.

-----------

You know as I was looking at this I was thinking how easy it would be to convert it to 1/2" 4 track or 2 track. Just need a set of heads...and make them fit the headstack assembly.

 

[SteveM]

You know as I was looking at this I was thinking how easy it would be to convert it to 1/2" 4 track or 2 track. Just need a set of heads...and make them fit the headstack assembly.

That thought crossed my mind before. It was 600 something per head so it didn't cross my mind again.

EVM I'd scan and send you that motor assembly schematic but my scanner just crapped on me today! as I was trying to scan something.

 

[Dr ZEE]

my scanner just crapped on me today! as I was trying to scan something.

oh boy
*****

Put a scope on the feelback from the motor and rotated the shaft. Looks OK I see a sine wave from the motors tach.

I'm clueless here. Question - you've checked "feedback"? What if you check the DC-terminals of the motor, spin it up. Should not it generate some DC if its ok, and if it's 'dead' - it generates nothing?
Here's the "exhibit"
Or am I saying something ridiculous here

 

[evm1024]

no need.

Thanks for the thought Steve. The motor is toast and I'll need a new one if I'm going to make this deck work. (well thats not true....)

The A-3440 uses the same capstan servo circuit and I have the schematic form there.

I did a few more tests to be sure that the servo was working and then called the motor bad. I pulled the motor. 12 volts to it and it did not run.

Now it gets interesting......

I opened up the motor and found that it had gotten so hot that it melted the solder that connected the windings to the commutator board. The centrifical force threw this melted solder to the sides and thus the motor stopped running. The wirewound series resistor in the motor wass also toast. Who knows what value.

I'm guessing that the deck was overloaded at some time (pulling sticky tape?) and run that way for an extended period. This caused the motor to overheat and melt the solder (somewhere around 650 degrees). Some of the solder shorted out the commutator and blew the drive transistor. Tape stops and off to the shop it goes. It gets cleaned up and the drive transistors replaces but no motion. the tech says that you need a new motor and the owner says too expensive where it gets sold on E-Bay to the guy I got it from.

Just for fun I resoldered the windings and put a 47 ohm resistor (should be 1 or 2 ohms) in the motor and round and round she goes. I would not trust it and no need to put it back in the deck.

So I have a choice to make. I can order a motor form EBay or Teac (oh how much would that cost my wife asks.) Or I can part out the deck. I really have no need for an 8 track. Sell the usable heads, sell the channel cards (BurrBrown opamps installed of course), keep a few VU meters for a mic preamp and sell the rest. Then I could buy a motor and turn it into the 2 track....

descisions decisions decisions.

 

[evm1024]

Oh here is a photo of the heads

record good reproduce badddd

 

[evm1024]

oh boy
*****

I'm clueless here. Question - you've checked "feedback"? What if you check the DC-terminals of the motor, spin it up. Should not it generate some DC if its ok, and if it's 'dead' - it generates nothing?
Here's the "exhibit"
Or am I saying something ridiculous here

Actually a good test Dr Zee. Being a permenant magnet motor it would work as a generator. They are not brushless by the way.

 

[Dr ZEE]

Good work!

I would not trust it and no need to put it back in the deck..

why not? Is it really that hopeless.? I mean, since you've cleaned it up, replaced components and it runs - what would make you think that it's an "unrelyable" motor as is now? Just curious.

I've found these guys somewhere in Montana, have no idea who they are, looks like they are selling loads of "body-parts" of fallen heros. 129 bucks for the motor with the board here in US plus 10 bucks shipping.

Does 'teac parts' still sell them still? How much?

 

[evm1024]

Good work!

why not? Is it really that hopeless.? I mean, since you've cleaned it up, replaced components and it runs - what would make you think that it's an "unrelyable" motor as is now? Just curious.

I've found these guys somewhere in Montana, have no idea who they are, looks like they are selling loads of "body-parts" of fallen heros. 129 bucks for the motor with the board here in US plus 10 bucks shipping.

Does 'teac parts' still sell them still? How much?

I know those guys. Got some knobs from them once....

The problem with the motor is that the overheating and spraying solder tookits toll onthe brushes and commutator contacts. The contacts are very rough and I would expect a very short life for the brushes. Plus the windings wire has lost its annealing and has become brittle. It may break soon here and there. And some insulation has burnt possablying causing a short in a winding which leads us back to overheating and early failure.

That motor could last a few years or fail in the first hour.

But you made me think about it so I guess I'll put it back in and see what is on those reels of tape. (both are NOT sticky I might add)

-ethan

 

[Good Friend]

Wait

Wait, 38s can be switched to 7.5? Where is it inside? Is it easy to get at? Is it something that you have to tweak or just a switch?

 

[evm1024]

yes qualified

Wait, 38s can be switched to 7.5? Where is it inside? Is it easy to get at? Is it something that you have to tweak or just a switch?

The servo board is the same as 32, 34 and who knows what. It comes fully populated with parts for both 15 and 7.5 ips.

In the photo you see the 2 gray wires. The lower (in position 4) and upper (in position 2) are the speed select (selecting high 15 ips) There is no wire in position 1 (top position) which would set the motor to 7.5 ips.

Please note that this does not select 7.5 ips anywhere else in the deck (eq and so on). Non trivial but do-able if you want it all to come out right. (same cards in a 34B for example)

--Ethan

 

[Good Friend]

thanks

Nah i dont think itll work for me, i mainly wanted it for special effects, not to be semi permanent. Thanks though!

 

[evm1024]

running

OK, so I did rebuild the motor (who knows how long it will last ) and reassembled it. (Thanks Dr Zee) Here is a photo of it in operation. The 2 tapes I got with it have some tracks on them and it sounds good on the sync head. The reproduce is gone beyond relapping.

Does some kind soul have the center hub from a 1/2" reel that could send me for postage? (The plastic center of a pancake that the tape winds on) I'm using (2) 1/4" centers and it is just too deep to let the hubs lock it down. I figure that this is cheaper than buying a takeup reel.

All in all I would say that this deck has potental. Just needs a motor that I trust and to be calibrated. Then you might want to toss in a new head (move sync to reproduce) and a manual.

I don't know what it is calibrated to but the tracks on the tape are pegging the meters. +6 and above with no obvious distortion. (Some kind of techno on the tape)

A few bucks and a few hours and it is usable. Not bad. Still might come up with a set of mods to allow 7.5 ips and 30 ips. Looking for 1/2" 2 or 4 track heads (used but usable) cheap. That would be a project.....

 

[evm1024]

Motor lifespan

Well know we know. the motors lifespan was about 30 minutes. It is dead. I'll have to take a look and see what it is this time.

Still it has been fun!

 

[Dr ZEE]

ahh crap

you know what's funny, as I was reading your first reply (that it runs ok) in e-mail notification I thoght: "Ohhh, cool. Now you can recreate the failure and find out what exactly happened and how the crew members died." ... I guess that's what you've accomplished .
Post what happened.

 

[evm1024]

New motor is in....

....and installed. The deck is running fine. The known problems are a bad reproduce head (but that is not too important), 6 of the VU meters lights are burnt out, may need speed calibration and general calibration.

I've not recorded anything on it yet but I expect no problems there. I may do the Burr Brown opamp replacement on the channel cards but then again I may not.

I do not expect to buy a new MRL for this. I'll keep an eye on eBay just in case. I would like to know what it has been calibrated to. Anybody out there want to take their deck and lay down a few minutes of 1 KHz tone for me. (Hm, how to ship???)

Right now I'm looking at this as more of a engineering project machine.

I could work out what you would need to do to run it at 7 1/2 ips. Everything should be there just needing switches and a few wires.

Or at 30 ips. the question there would be how would the motor like it.

Or the 1/2" 2 track or 4 track (send heads and I'll do it)

Or convert eq from NAB (thats IEC1 if I recall correctly) to IEC2.

So many things to do. Perhaps it would be better to just record something with it.

Oh, oh. Anyone glue LEDs to the meters? I'm thinking that you could attach an LED outside the meter case and do away with the lamps. Anyone have a few spare meters to test this out on?

So many ideas and so little time.