TASCAM 238 ......is this machine about to have problems?

altruistica

Member
I'm just uploading a video I've made to document a problem I have with one of the two Tascam 238 machines I recently purchased. One of the machines has had the capstan board replaced (although the repairer didn't select the 'double-speed' option of 9.6cm on the board by unsoldering the 4.8cm position and soldering the 9.6cm), so this machine still needs fine-tuning where the actual record and playback speeds match. The other machine has a tired looking capstan board compared to the new board and the tests I've just done seem to confirm that it may well be on its last legs before the 'runaway' capstan issue that I've read plagues these machines.

The test I've done is this. I took a 440Hz signal from a Roland synth, a simple sine wave. I recorded it on TK7 for the new capstan board machine (let's call it Machine 1) and then swopped the tape over to the tired capstan board machine (let's call Machine 2) and recorded the same on TR1. I could monitor the pitch of the tone through the machine on Korg Tuner. Now I think I'm right in thinking that the monitored signal going in to the tuner (ie. from the phono out of the various track outputs) is just a copy of the input signal and not what is actually on the head, yes? When I replayed TR7 on M1 (machine 1) the tone was a few cents flat at the beginning but by half-way through the tape was bang on in pitch. I used the vari-pitch just to fine tune this difference as seen in the film. The pitch on this machine was constant and didn't waver at all during playback.
Is this because of the new board or is something else involved in controlling the speed?

When I replayed TK1 on M2, I was very surprised. The note A when monitored on the tuner was now a very sharp B flat! So the machine was playing back at a different speed than it recorded. By about half-way through the tape, the pitch was still slightly sharp and about three-quarters of the way through the tape the pitch was about right. What was easily discernible though was the pitch falling from a quarter tone sharp B flat through to an in-pitch A over the length of a double-speed SA60 cassette (15 minutes).

Does this all sound like a failing capstan board which can no longer control the speed?

If so, do you think fitting a new board will solve this problem? The boards are advertised on Ebay here


and also here


Notice the different coloured caps?.....I think the new board the M1 has the yellow caps.

I don't think my soldering skills are anywhere near good enough to replace the caps on the original board as the whole board is only about 4 inches square....though if I do buy a new board, it looks like the only soldering needed to be done is around the centre of the board? Can anyone confirm this?

Here is the video:

 

sweetbeats

Reel deep thoughts...
Only have time for short reply.

The caps on the servo board are surface mount originally, and the PCB material isn’t glass fiber…easy to lift traces when desoldering etc. complete and utter PITA speaking from directly related experience. I recapped the servo board in the last 238 I owned hoping to fix the runway “jet engine” capstan motor. I failed. I ended up buying a brand new assembly from Teac back when they still had stock. Worked like a charm.

So…I can’t recommend trying to recap it yourself although if you have the option to purchase a refurbished unit with a guarantee, what’s the harm in trying to fix yours? I think that’s what I might do if I was in the situation again…try one more time. I’m kinda dumb that way.

On the issue you are experiencing I don’t assume that’s the servo board. It might be, but it sounds more like pinch roller failure…either the roller needs replaced (is hardened or slick) or the pinch roller pressure needs adjusted. The tension control isn’t as sophisticated as an open reel machine, and as the tape pack shifts so does the torque…not a lot, but enough that it could effect a gradual shift in tape speed over the course of the tape play if the pinch roller can’t keep the tape positively mated to the capstan shaft.
 

altruistica

Member
Thanks for your thoughts Cory. I wanted to pick users' brains about what factors might be in play with this problem. I need to look at the service manual to see if there is an adjustment somewhere between the speed of the capstan in record and the speed in playback. If the pinch roller was at fault, are you saying the pressure exerted when recording would be different than playback? For the pitch to rise on playback, I'm assuming the note A is being recorded at a slower speed that it is when it is being played back, hence the rise in pitch. It may well be worth trying to find a new pinch roller and doing the board replacement especially as I plan on keeping the two 238.
 

skywaveTDR

Active member
The speed in the deck has no difference between play and record so you don't have to look for it as I have never seen such a thing.
I have recapped about 135 motors in decks as well as repaired them and the worse one I get are the ones that amateurs work on. If you are not able to remove SMD parts then
don't do the work as you will make the board worse. Buy that stupid board on E bay is a waste of time- it has no coils on the bottom and it is build the same poor way that the first one was . Rule is to GET RID of SMD caps. I only put through hole parts on my motors and they work great. C 2 is also replaced by a Polystyrene cap which is far more stable.
IF you guys want real answers, talk to the guy who fixes these not guys who guess and spend time making stupid You Tube videos.
 

sweetbeats

Reel deep thoughts...
@skywaveTDR

I for one value your presence here as well as your breadth of true experience working on these machines and your institutional knowledge as well, so thanks for bringing that here. I just consistently wish you weren’t so condescending at the same time. Making people feel small is never the way to earn business. I’m sure guys like me frustrate you. I guess I’m just saying your frustration is often louder than your wisdom and I wish it was the other way ‘round because you are a tremendous resource. I’ve purchased parts from you before and referred many to you and I’m going to continue to do that for a number of good reasons. I guess I’m just hoping you might consider softening your approach.
 

skywaveTDR

Active member
How exactly am I condescending. People in general like my direct approach and they have told me this. Why does stuff have to be sugar coated. I do not intentional make people feel small and if they do it is their wrong perception. Why would I be helping people over the years in getting the deck fixed with over 17,000 posts on different forums if it was my intention to make them feel small? While it is true that there are a lot of crooks out there and people selling things on E bay that you simply do not need. I might have a harse word for them but why collect money for a thing that is taking advantage of people when it just is not called for. One example is that guy that sells a complicated board with chips on it that correct a problem in a 122 Mk III when all you need do is issue a play command through the remote socket on the rear of the deck one time? It is clear that in the presence of certain Technicians that if I do not make the suggestion strong enough that the person will miss it.
 

skywaveTDR

Active member
The problem with motor boards is that people go to the first level and say if they do not fix it that way then they give up. We had tons of mistakes made by all kinds of people in trying to get to the Moon but we finally did it without giving up. One of the things people skip is the C2 replacement and then the other thing is the lack of repair of the board when compromised foil patterns are seen. All you need to see if there is a break is a DVM and see if the continuity is there. So as I tell my trainees, don't let a circuit defeat you push ahead and the guys who do fix these are the one that stick with it. All kinds of things in life are not easy. Gerhard in Florida has only about 1 years of training and he is fixing stuff very well and customers love him. I told these guys the reason I train people is I can not do it all myself as there are thousands of decks out there broken. If you have trouble like I said in another post don't get discouraged but E mail me or call and I will do what I can to help.
Dean in Canada was all beat one time working on a V900X and it is not an easy deck to work on. He was going to send it to me but he tried one last time and he fixed it. I don't need more work, I need less so if I help you fix a unit then I don't have to work on it.
 

altruistica

Member
Thanks for the replies guys.
You must remember the USA is a helluva big place.....350million people compared to England with 55million. Finding anybody alive here that can fix tape recorders is difficult. I had to travel 250 miles with the Fostex G24S machines to find someone who knew what they were doing. Tascam is a point in question. I would probably be still using the SX-1 that I bought secondhand in about 2008 had it not being for the fact that there is no support from Tascam in the UK for these machines. The work is farmed out to contractors. AKAI went the same way. So finding people qualified to fix these things AND at a price that doesn't make repairs totally uneconomical and unfeasible, is difficult. I don't expect people to work for a pittance, but I do realise that for every chargeable hour that a technician puts on the invoice, they've probably spent two or three times that amount dismantling the item and maybe another two or three thinking about the problem especially if a fix hasn't cured the problem.
Whether we got to the Moon is a debate for another day.......just like Covid.......they only tell you what they want you to hear and what they think they can get away with.....for me the ridiculous Moon buggy says it all.
If the answer to keeping old gear running is spending the time genning myself up enough to open up a repair shop, as I approach 60, that ain't gonna happen. I have too many other things I want to do (like record my music) to invest that kind of time. As I understand it (and forgive my ignorance), the runaway capstan board issue, is because the SMD caps leak and also in doing so ruin the board. How long does this take to happen? Well if it happened after say five years, then Tascam would have been in-undated with complaints. If it happens over ten, then people may just sell the machine and move on. It's probably difficult to guage how long, because these machines came out just when all things analogue were being discarded for ADATS and DA88. If the fault lies elsewhere with the runaway issue, then parts may be unobtainable and then you are in the realms of manufacturing new parts, which with the rise of 3D printers may well keep the machine in play.

As to Skywave saying he has never seen a difference in machines' speed in rec and playback, I would like to see others replicate my experiment. Put simply, you get a tuner (or I suppose you could use a computer), record a tone or a track. Afterwards playback the tone and see if it matches the pitch you were sending it. It strikes me because we're dealing with magnetic tape and motors, there will be some fluctuation....even if it is at the one cent margin and within the tolerence of the machine. If, what I saw with the machine that has never had the board replaced is found on other machines (ie record a note A which replays at Bflat), then maybe this is an early warning system that the runaway capstan issue is around the corner. Of course I haven't a clue how the logic of the chips control the board, but I'm just going from the assumption that a board working correctly results in the note A being replayed at the pitch A, and then the anecdotal evidence that people discover they have the runaway capstan issue when they put a cassette into the machine (speed of recording known) and it plays back at some super duper speed.

As to the validity of buying the replacement board, once again, it is one of economy. If you're saying that the coils burn out or are part of the problem of the runaway capstan issue, then without them it is maybe futile. But if you're saying that it's pointless buying the board, because you still have to then solder the coils, then I think you're wrong, because I think I could solder the coils but maybe not be as successful tackling the SMD caps. This would then give me another five or ten years (we don't know because it was never logged) before needing to sort out the situation again. If I could find a technician locally that could do this kind of thing for the price of the board, then of course I would.

With the state of the world as it is at the moment however, to be even contemplating what we will be doing in five years time is ridiculously difficult to imagine. I can understand Skywaves' frustration at the amount of work he sees by hacks like me and can only say I'm trying to be less of a hack these days by being realistic about my own skills and seeking advice where I can before rushing in.

Dare I mention?.......the boards arrived today.....but I've got a Promaster campervan that needs sorting so this one will have to wait 'til another day.
 

skywaveTDR

Active member
Many a person who contact me due to distance and the problem they have to fix the machine on the spot. I had a 122 Mk II in the Mal Dives that I helped the guy fix over the phone. At the end I had to ask where is the Mal Dives then on a World Map I found it. Not likely the guy would be able to send it to me. I am near Chicago.

New board- The reason I find the new board ridiculous is that they made it the same way with those junk Chinese SMD parts so even if it did work, and I have a client that it did not even after he transferred the coils. I told him that I just prefer to fix the old board which we know one day worked. Most of the time they do work.

Speed differences between modes? Well you need to think of this logically. What is the difference in play mode to record mode? Well the Bias Oscillator is on. Well how can that affect the motor- well the only thing I can see is the power supply. Does the power supply change voltage due to the addition of the bias oscillator? Well not normally but I can state that I have taken off the power block off a 238 and seen some solder joints that are not good so maybe yours is due for a resoldering. It is not that hard to get them out but then you have to take the heat sink off and go further. I really do not like the soldering I see on most Japan decks as it is mostly wave soldered which never passes aerospace grade or quality- just too little solder on joints for me and they are not shiny like they are suppose to be.
The reason the new board will not work by itself is it has no coils to drive the motor. So then the coils have to be put onto the new board or you could say it the other way around. The wires to the coils are very tiny and have been stressed already and they do break on occasion even when not transferring them. I had to take one off and find the end and then reattach it which is kind of like heart surgery. It is possible to do but it is not my first choice. So to me even the new board would need to have the SMD parts replaced with the 105*C caps I use which are very much better than that throw away SMD part. Companies like you to use SMD parts as they are throw away, cause failures and they the capacitor companies give you so very little for your money- they should probably give them away for free for what you get- even then I don't want them. SMD is a code word for JUNK. There is a reason I hate that kind of part- it provides very low reliability and is not long lasting.

My motors do not look so fancy with through hole caps mounted on the board but they do work and reliably so who will be looking into the decks insides anyway? The speed drift is caused by a single part that was even determined in Europe with the guy who used a straw to prove how unstable these are. Well when you use garbage parts you get garbage results- having some knowledge of electronics I put a Polystyrene caps where the ceramic C2 was. So putting a much better part that the ridiculous cheap ceramic part probably 100 times it cost results in a case where the motor stays as close as it can be without a crystal reference.
The audio cards made use of Marcon 100uFd caps and I typically change those- if they are shorting partially or leaking that adds more load to the power supply and being these were made for profit then the power supply might not be that much more capable to handle additional load from when they were new. I think your speed issue might be related to the C2 in my experience. Any dark colored foil traces should be wired across with small wire wrap or telco 30 gauge wire. The foil may not be open now but the dark color tells you that the foil is already affected by electrolyte spill and might open one day. If the wire is point to point over that it will not matter.
 
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skywaveTDR

Active member
There are private people in the UK that are technically qualified but you need to find them by connecting with a group they are on. The big problem is the need for the MXT test tapes as when you work on these you need to calibrate the speed not with a 440Hz signal but the MXT111 which right now only come from Genn Lab. Yes the UK does not have as many people but who figured out the Enigma machine in WW2 despite of that? Fewer people does not mean less capability. I really do not have a list of guys other than Alex and he is not working on decks anymore. He was a tape deck design Engineer and if anyone can fix a deck he can- he is known on other forums as ANT. Mr Nikitin is a real Engineer and I sometimes consult him as his answers are real and can be verified. Check out other places like Reel to Reel Clinic on FB and there might be a new person that fixes decks around your area. IF not then you are it and will need to connect with me or Jim Finch to get answers to fix it where it is.
 

altruistica

Member
Thanks Skywave for those very in-depth replies. It is much appreciated. There is a tech who I used to repair my daughter's i-Pad who can solder / repair tiny stuff, so when the time comes I may reach out to him about transferring the coils. On the machine I bought from the Netherlands, a tech has done just that as you can see how the end wires of the coils have been beefed up with solder. It's interesting to see the 'mods' techs have done in the past to the IC near the 4.8cm speed point as outlined in an earlier comment.
Are all SMD caps junk, as I seem to see them all over equipment these days, or is it ones just from a certain period?
 

skywaveTDR

Active member
I call them all junk while there may be some better one the ones that are substandard are from China. I myself find nothing good about SMD parts and if you look into how long they are to last you will find out the parts are put into throw away products. If you have a $1500 I phone they have those garbage parts in there but they had to because this is a size issue requirement. Still if you want anything to last more than 3 years then get a product with real parts in it not SMD. There are Through Hole parts that have lasted 30-50 years but there are no SMD parts that last very long- they are made with a cheap and substandard method- ask any of the manufactures if they have a 10, 20 30 year warranty on any of that junk. I would be surprised if they had a 2 years warranty. I tend to stay away from junk as I don't have time for it and thus my reluctance to work on Akai decks.
 

skywaveTDR

Active member
I watched the video most the way through as it was giving me headaches with all the unfocused close ups. First speed is tested with 3KHz not 440Hz and then if you have unrepaired products made with those $.001 C2 parts how can you expect it to work right at all. The C2 needs to be a Mylar or a polystyrene like I use. It is well known from the guy in Europe that used the straw to find the problem and what he was changing was temp and humidity to the C2 which is a junk part. He conformal coated it but that was just avoiding the problem rather than fixing it. These are not crystal controlled and one day that might be possible with the right engineering applied but I have enough work to do the way it is and so I will not move on that kind of idea right now. Usually fixed correctly the deck work well after that. Watch out fo the pin switches near cam motor they have been causing decks to pop out of record or play mode so if you take he deck apart to spray them with Deoxit then they work well again. There are no military or even high grade parts in the deck- they were made to work for a few years and then be replaced which is the manufactures thinking of all devices.
 

sweetbeats

Reel deep thoughts...
I call them all junk while there may be some better one the ones that are substandard are from China. I myself find nothing good about SMD parts and if you look into how long they are to last you will find out the parts are put into throw away products. If you have a $1500 I phone they have those garbage parts in there but they had to because this is a size issue requirement. Still if you want anything to last more than 3 years then get a product with real parts in it not SMD. There are Through Hole parts that have lasted 30-50 years but there are no SMD parts that last very long- they are made with a cheap and substandard method- ask any of the manufactures if they have a 10, 20 30 year warranty on any of that junk. I would be surprised if they had a 2 years warranty. I tend to stay away from junk as I don't have time for it and thus my reluctance to work on Akai decks.
True dat.

I seek out gear that is all through-hole design. Through-hole parts are starting to become limited. I think it will be a long while yet before it is a problem, and I think there will likely always be a supply of common parts, but companies are phasing out manufacture of obsolete through hole parts. I purchased a considerable supply of through-hole parts for this reason.
 
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