Tascam 38 head issues

As the deck is on it's back channel one in all Teac product is at the top of the head. Doesn't matter if 24 track or 2, it is always at the top. There are relays that fail in the 38 cards. The same circuit is used for Sync and Repro so if one works and the other does not the DIP relay are the likely suspect. The coils seem to open up on units and I remember them being pins 2 and 6 on the Dip relay. I put sockets in the unit so that when it happen again the card is extracted, a new relay is easily plugged in plus it does not damage foils when changing the relay the 3rd or 4th time.
Change cards around and if the problem follows the card then relay, if it stays then motherboard or connectors.
 
Hi Skywave,
Thanks for your reply and info. I've found a few PCB120 boards for the Tascam 38 on ebay. My strategy was to buy one (or two, about $28 each) and replace the whole card. I could then work on bringing that card I removed back up to spec and have a replacement that I know is OK. That way I'll have a couple spares. I bought the deck in new 1983, so if one card is faulty, others may soon follow. Make sense?

I found this pic on the web. The front of the deck is facing the bottom of the picture. Therefore, the card for channel 1 would be the one at the bottom next to all the wires - right?
Tascam 38 open bottom.jpg
 
Those people that think a card can just be switch in with no ill effects do not know tape decks. There are bias traps to be adjusted to the heads that the card is plugged into and also the deck has to be calibrated in that channel when a new card is put in. People get the idea that everything is plug and play like in a computer but it is never that way in analog as many parts have to be adjusted to other parts in an assembly that all things work together to reach the result. There is nothing wrong with having a spare card or two but to think you plug them in and go is not going to happen. The pots at the card edge are also kind of fragile and adjustments can be made to go off mark when the card is handled.
Just like the head tracks, when the deck is on it's back the channels match the head track placement so the top most card is channel one and then down the way where the last card is channel 8.
 
To work on this model effectively you will need to have a service manual in hand- paper is preferable. Either an original one or the one from Stereomanuals.com is what I use. If you had a manual the above question would not have been asked. The need for a MRL alignment tape is also required as well as an external switch system and a meter like the LMV181A (Leader AC millivolt meter) and a bunch of cables. Too many people send me questions with no test equipment and alignment tapes and in 99% of the cases they are not successful in correcting the problems not to mention they make a month long job out of a three hour one.
 
Hey Skywave,
Yes, I have the original service manual and schematics. I'm 66 and was more in the music and production end rather than the tech end of this stuff. My friend here in Boise has the test tapes and all the test equipment (he is 70 and worked at HP his career and still has is own shop for repair for tape decks, stereos, etc.). I'm going to swing by his place this week, have a cup of coffee, and go over this with him. He has worked on Tascam 32's and 34's so I'm sure he can look at my 38 as well.

I thought I was on to something with just replacing the audio card, but like you said, it may not be the answer after all. Oh well, carry on!!
Thanks.
 
What does "checked out" mean?What was done to make it work? Does the problem follow the card? If not it still sounds like bad solder on the motherboard.The signal from the R/P card leaves and goes to the M/B, then splits into two legs.One goes to the output jack the other goes back on the card to the meter amp. which is on the R/P card then back off to the meter.Time to take it to someone COMPETENT if you can't read schematics and troubleshoot logically.
 
wkrbee,
Thanks for your input. Actually we are already doing all the steps you listed in your email, but thanks in any event.
 
These are not that hard to resolve problems on. On occasion the Technicians- manager at Teac had one he could not figure out. Where did it go? He gave it to me. I figured it out but it took some doing. Most of them were not like that. The vast majority of the problems are widely known such as the DIP relays and solder feed through. The problem comes when people starting on this for the first time do all kinds of abstract things like replace boards and other unusual things that when they mention them under my consult, I try and set them straight quickly. There are some though that still over complicate the repair task by not staying focused. If they do this they usually cause a door stop machine. Pick a problem and resolve it and then work on the next one until all are gone. This is how I did it at Teac and on my bench during my own service business. The use and demand of these decks has not declined as I have had up to 160 unit in repair recently. Not all of them Teac and Tascam but having worked on some lesser designed stuff I wish it was.
 
Hi Sky,
Thanks for your help. I'll you guys posted as to my progress.
Cheers!
 
As the deck is laying on it's back which is how I work on most of these, the track one is at the top of the head and track eight is near the face deck of the machine. On the sync problem the relay switches from which head is being used to the same circuit in the deck so if the bad cap is the reason it will affect both functions the same. If the relays have been changed OR the problem follows the card the relay solder joints and the connector pins might need resolder. If the problem stays with the slot, then the feed through pins will need looking into as in resoldered. I get to work on a 38 tonight. A3340S is on bench now.
 
Channel one on all Teac and Tascam decks is at the top of the head as the deck is on it back or the track furthest away from the face plate. If the play channel works on 1 then the amp card is not the problem as the same signal goes through that circuit only from different heads. I suspect the motherboard connections, relay or maybe the head socket connection. Keep in mind that track one at the edge can give some varied results when recording as the edge of the tape and with this track width the 1 and 8 are the least stable tracks.
 
Hi Skywave,
Again, thanks for your help - much appreciated.
All of the tracks are working now in both sync and repro mode. One thing I've noticed though, volume difference between sync and repro on playback. The tracks play a bit softer volume when the repro head is on. Thoughts??
Thanks,
Richard
 
There are both Repro and Sync play levels on the audio cards. They both are adjusted with the operating level of the alignment tape. They should not be different.
 
Older post but I enjoyed reading all of it. I had a magic 38 and two mx2424's. I sorely miss both 38 and mx. Loved my 38 even with different issues here and there it had mojo.
 
Channel 1 is the top of the head as looking at it from the bottom of deck as in on it's back. The question is- does the problem migrate with the card? If it does then the repro sync head relay probably is it. If not then the motherboard solder through joints have been issues in all kinds of problems. I take the back panel out of the way and get my work light in there and start to solder all the pin through locations- I do it with magnifiers on as I like to see all the detail. With the board in the deck it is hard to do the job but it can be done as I have done it a number of times.
You can even trace the schematic so that you know what card pins it goes through and find the
problem with an DVM. I have even had some crimped wires on the connectors break contact so that I had to take them out and solder the wire to the pin. Crimped wires only last so long- never as good as soldered wires. It is rare though. the same circuit is used for the two function and the relay is where they switch what head is being put through. One of the Omron dip relays again. I don't know how many of those I have changed over the years- I think a lot of them.
 
Channel 1 is at the top as the deck is on it back- often time with bottom propped up due to cables- I use a 2 X4 Piece.
Anyway, the support bracket needs to come out and I would put a socket for the sync relay and then once that is replaced that would be then easy to change. Trade cards around again and see if the problem follows card- if so relay or solder joints, if not then the motherboard need resolder on the feed through points and if this is not taken care of it will haunt you for a long time. I don't thing Deoxit is the answer here although you can try it.
 
OK, A person bought a 38 on E bay and we picked it up for him here in Chicago which is where it was. The deck had sync head function problems. It was determined that there is a relay that grounds the sync head on the right side of the board. This relay is what was found to be bad on many of his cards- I think 2 or 3 did still work but then I don't want to have to be shipping this back and forth so all 8 were changed. The original Omron relay was not possible to find but I did find a Potter and Brumfield relay that is the replacement. They have them at Mouser. If you need the part number let me know. The feed through soldering is a real pain and if that does not fix a problem then you need to look elsewhere.

As time goes on an old post may have additions added to it that then bring light to further discoveries that are offered for solutions from a Technician on the front line. This is why I added this.
 
  • Like
Reactions: Caveman
Channel 1 is at the top of the head away from the front panel of the machine and has been that way on machines I have worked on since 1982.
 
  • Like
Reactions: Caveman
Just as a warning to some that pull these out of the closet after a long time. The deck needs to be inspected before trying to run it. The last one I worked on went higher in price as the very lose belt jammed and blew out two 3 Amp fuses and at that time burned up two fields of the rotor of the capstan motor. This then requires a new $150 motor and they are going up all the time. I heard that the BR20 motor which can be used in this deck is $170. It is best to be cautious and not burn up motors and other parts when the repair bill would be much lower with just a belt and lubrication and maybe a new Pinch Roller on this model. The tension arm cylinders seem to also be sticking up so need to be removed and cleaned and new Silicon damping solution applied. I don't like having to do them but that is part of the job.
 
  • Like
Reactions: Caveman
You must log in or register to reply here.

New posts

New threads

Members online

No members online now.
Total: 21 (members: 0, guests: 21)
© 2004-2024 TASCAM Forums. Forum software by XenForo. This site is not affiliated with TEAC or TASCAM.
Top Bottom
Back