Tascam 58-OB Story...

[analogkid]

Sadly I tossed many MANY product brochures from the early 80s..... who knew that advertising junk would be worth money some day?




AK

 

[sweetbeats]

I totally know what you mean, and I'm sure you'll agree with this next statement too, but its not the monetary value that gets me...reading the 58 brochure really gives me perspective on what the 58 was designed for and where Teac's head was when the designed it and put it to market. It helps to tell the story and I like that.

 

[sweetbeats]

If they could talk...

58: Hey...You're new here...what's your name?

234: Oh hey...I'm 234...what's your name?

58: I'm 58! Nice to meet ya...uh...welcome!

234: Thanks!...hm....yeah....

[long pause, mildly awkward]

58: ....so-uh...anyway...I couldn't help noticing your left side there...what happened to you?

234: Oh yeah...that. When they boxed me up to send me to this place they didn't put enough padding around me and the trip was pretty rough...not sure what's next for me y'know? I got banged up pretty good...so, uh, back atcha yeah? I couldn't help noticing...yer lookin', ah...not so good yerself. Same thing? You get banged up in transport or somethin'?

58: No-no, not me, not like the guy in the other room [faint moaning heard from adjacent room wherein lay Parts 58]...nah, my owner, now yours, was working on me and carelessly stuck an extender card in me all wrong...fried some of my components and here I sit. That was months ago. Anyway, good luck to ya!

234: mommy...!

 

[sweetbeats]

Got the Control PCB out...

While I'm waiting for the rest of the caps to get here for the main PSU PCB (recall I removed the caps off of it eons ago...Its ready to be recapped...caps should be here in a couple weeks) I thought I'd recap the Control PCB. 12 connectors and a couple screws later (and one soldered in wire......there's always at least one...it couldn't be as easy as just pulling the connectors could it? ) its out. I'll inspect for any cold solder joints and make sure all the connector pins are happy lookin'. There is a little PCB called the Delay PCB that is siamesed onto the Control PCB...they are lapped together by a couple test-point pins...seems like an afterthought...anyway both solder joints have broken loose so I'll repair that too.

Once the PSU gets recapped (and I finish recapping the little PSU for the balanced I/O and put in the new +15V regulator) then I can:

1. Put stuff back together (leaving things disconnected)
2. Test that the PSU is producing everything that it should without fuses blowing
3. Start hooking systems up one-by-one to see if everything is happy

 

[mastercontrolme]

Man, i'd love to have a 50 series machine!

 

[sweetbeats]

Control PCB recapped...almost

Okay. I sound like a broken record if you've been reading my other threads...I'm awaiting some back-ordered caps that should be here in a couple weeks, so I got the Control PCB recapped except for one.

BTW, another discrepancy between what was put in at the factory and what is in the parts list/schematics:

• C20 is actually 2.2µF, not .68 as shown in the parts list (but 50V is correct)
• C23 is actually a 25V cap, not 35V as should in the parts list (but 47µF is correct)

I believe the values are correct in both cases on the schematic for the Control PCB, but I don't have a good copy at hand at the moment...

Anyway, after all this recapping I've been doing on the M-___ I figured this would be easy, and then I noticed that the Control PCB is double-sided. In other words it has traces on the both sides and in many cases the cap is soldered on both sides of the PCB. So it was a good challenge and learning experience. Everything came out fine...I think getting the soldering iron in where it needed to be without frying other stuff was the most tenuous part of it, but everything came out fine.

Here's the component side:

Here's the bottom side:

Replaced the one cap on the Delay PCB too.

 

[mastercontrolme]

Hey Cory, did you have trouble changing the caps on the boards? Is the board double sided? I want to recap and maybe swap opamps in my 42, but the board looks intimidating...

 

[sweetbeats]

Yeah, it required a little finesse, but ultimately it wasn't too bad for me...

I've been thinking about putting up a post with a video showing some basic soldering/desoldering techniques...I've thought of doing that for awhile. Sincerely not that I'm an expert, but if a picture is worth 1000 words, a video can be incalculable. I know how much I would have benefitted from seeing a video of demagging or adjusting tape tension when I was struggling through all that...Folks were so patient and helpful here and all their posts would have been just as helpful, but there is something about seeing a process in motion. We'll see...but some essential bits for working on the double-sided PCB's, or any solder work for that matter is to:

• have a healthy solder vacuum pump (I just cleaned mine out for the first time and applied petroleum jelly to the seals and its got a kick now! )
• have a good iron (I use one of these per evm1024's recommendation and I can't tell you what a difference that alone has made. I realize the Antex M isn't fancy...no heat adjustment, no stand/holder/base station or anything like that...it is simple and basic but boy it heats up quick, is so easy to handle and has really made a difference in my solder jobs...nice and compact and the tip temp has worked for everything I've thrown at it with working on my Tascam stuff
• keep the tip dressed (shaped...file it back to a chisel when it gets deformed)
• keep the tip clean (I use a piece of wet t-shirt material and wipe often, and I find that even if the iron sits for even a few minutes while I'm stuffing the next round of components it gets a thin coke on part of the tip so I scrape that off with a utility knife and then wipe before going back to work)
• prep your solder pads (tin them if needed, or if you are removing a component to put something new in clean the pad with iso alcohol after pulling the old part)

All the above basically serves to enable the heat from the tip to act quick and go where you are trying to put it; it removes foreign barriers to the heat conduction, and in that way the time the tip is on the work is kept to a minimum.

With that being said, for, say, removing a cap on a double-sided PCB I take my healthy solder pump in one hand and the clean tinned iron in the other and get both in close, apply the iron and as soon as the solder is molten I zip in there with the pump and get it good...I found last night that when done right the pump will even get some of the solder from the other side. So I do both on that side and then flip the PCB over and get whatever is left on the other side, and then I found it helped to trim the little bits of lead now exposed back on the first side...get a good pair of flush cutters at your local electronics shop. Another valuable tool. I paid $8 for mine it was well spent. So now you've gotten as much solder off as you can with your clean good iron and your healthy vacuum pump, and you've trimmed excess lead material. Now I go back to the component side and heat one of the leads up and rock the cap back to get that side out, and then heat the other side up and out it comes. Sometimes in a tight spot I had to just cut the cap out and then grab the lead that's left with some little locking scissor clamp thingies (can't remember what they're called) and then heat it up to get it out. Sometimes there's still solder left in the hole. I'd try one more time to suck it out but it was difficult, so I took a push pin to open the hole up. Be careful if you have to do that...the fiberglass PCB's are pretty durable and I found that the Control PCB (and it may be the same with your amp cards...its not with mine, but my 48 has the nicer material for the amp cards) has a really good coating over the traces that is burn resistant and holds the foil on nice, but I'd hate to have to repair a trace on a PCB like that...its just so tight, at least for my skill-level.

Let me know if you have any questions or if I can help. Have you had much experience doing solder work on PCB's? A year ago I'd had none, just building lots of cables and snakes, but I'm really comfortable with it now...made some mistakes (repairable ones) and got lots of good advice and help here so there ya go.

 

[mastercontrolme]

Thanks for the tips. I do have desoldering experience with single sided boards, I have recapped many components in my collection, but when I saw that double sided board, I promply put them back in! The main concern I have is damaging the traces. I use a desolder bulb and wick generally and it seems to work well. I will give it another looksee over the weekend.

 

[sweetbeats]

Oh sheesh...I don't think it'll be a problem for you, really...but I realy do like my desoldering vacuum pump...

 

[sweetbeats]

Getting ready to solder in the new caps in the main power supply...gathered them up last night. I have all of them except for one that'll be here in a week or two.

As I was looking at the innards last night I started thinking "now is the time recap other stuff in there too". Stop the madness right? The reality though is that (hopefully) at no other time will it be this easy to get assemblies like the input/output PCB out of there...its relatively opened up, y'know? So the main PSU is ready for caps, the secondary PSU is almost completely recapped, as is the Control PCB...Bascially if I get the input/output PCB recapped there are just a few odds and ends and I can get everything back together, and then as time allows and as it is needed I can start going through the amp cards. They are much easier to get to and remove than the likes of the input/output PCB... : Had to actually take it out the front of the deck...fortunately the arming panel is already loose. Anway, its out and I started removing the old caps last night. I'm about 1/8 done with that part.

 

[sweetbeats]

Bit by bit

Okay...finally got backordered caps in a couple weeks ago and got around to finishing the recap job on the 'B' PSU PCB...the little one that powers the balanced I/O:

Also got the balanced I/O PCB partially recapped...what is it with me running out of caps??? This whole thing was really kind of silly...I figured I may as well recap all the internal fixed PCB's as cheap insurance while I've got the whole thing opened up, then of course I looked at 72 little cans on the I/O PCB and thought twice but pulled it and decapped anyway...then started thinking "wait...am I even using the circuitry on this PCB since I'm using the unbalanced I/O?" Looked at the schematic and no...I'm not. Oh well. need 6 more of one type of cap, but lookit how tight this thing is...I know its not like soldering surface-mount chips or anything, but for this guy it was a little bit of a new experience...

Next steps in the coming weeks (since my priorities are on other things at the moment), put the new caps on the main PSU, and recap the rest of the stuff inside...not much really...I'll do the amp cards here and there as time allows since they are easy to remove and I've got spares of them.

 

[cjacek]

Man, that's a lot of caps, Cory!

I'm really looking forward to you getting that 58 back and running again. It's a really nice model to keep.

NOTE TO SELF: OK, so now I have Ethan if I ever need my heads relapped and Cory if I need something recapped. Cool, I'm all set for life!

 

[sweetbeats]

More progress

Got the PSU recapped and replaced that blown regulator that got cooked when I put the amp card in wrong (its the black one right above the green one next to my thumb):

Also recapped the Interface PCB...easy...4 caps:

And while the soldering iron was hot I recapped the dbx connector PCB (just a couple caps on that one), and the Function A and Function B PCB's...7 caps total on those two. OH! And I replaced the single cap on the Master Oscillator PCB, the main bias driver. Pulled the caps on the Joint PCB's. 1 each. Thought I had those but didn't realize earlier that they are bi-polar. The manual doesn't show them as bi-polar, so those will be in the next order of caps along with the one I'm still needing for the Control PCB, the 6 I still need for the IN/OUT PCB's, several that I need for the Capstan Servo PCB, and I will also order the caps needed to recap the amp cards. So as far as what I'm wanting to do before I put the whole mess together and see if it works its the Capstan Servo PCB, finish the IN/OUT and Control PCB's, and the Joint PCB's. And since I have them on hand I'm going to replace the caps in the reel motors. There are just one each...cheap insurance. That's 26 caps total remaining to put in outside of the amp cards and I'll get around to them eventually. Again, I figured since I've got the whole mess opened up I may as well recap it. Then it will be time to review Ethan's excellent instructions for systematically powering up the different sections of the deck, testing as I go to find out what else may be damaged.

 

[sweetbeats]

Take a good long look fellas...this is the Capstan Servo PCB out of the 58, and hopefully it is the only time you have to see one because it was a PITA to get out of the deck. The Interface, Control and Fuse PCB's have to be removed or moved out of the way as does the transformer (so you can remove the Interface PCB mount brackets) in order to get it out, and then it is almost impossible to get to the top two of 4 screws that hold the Capstan PCB to its mount...then three of the screws drop down into the cardbay because you can't get your hand in there with the screwdriver tip...it would be a whole lot easier if the deck was on its face. It would be great to do this work with it mounted in the CS-607 rack but the side panels have to be off to remove and reinstall the PSU PCB. I'll have to see if I can find a way to safely block it up when I go to put the Capstan PCB back in. It would be easier to access if the entire transformer shelf was removed but that runs full width...wasn't going there.

Anyway, here it is:

Its interesting...this PCB is much less sophisticated and tidy. The foil side appearance and finish is exactly like the PCB's in the M-___ mixer. Not bad or anything but the solder pads are tiny.

I'm trying to determine if the electrolytics are a special tolerance. I've never seen these light grey ones before. I'll do some research, but do they look familiar to anybody? I think the script says Rubicon. Hard to read.

This is interesting because there is no parts list or PCB layout in the 58 manual for this PCB, and the schematic is subheaded "For Graphical Purposes Only". Maybe they thought nobody would be stupid enough to pull one anyway...well, that clearly has not stopped me in the past.

So anyway, I got the caps pulled from it and filled in the blanks on the schematic for several missing values (several of the caps on the schematic have no voltage spec...)

I also pulled the reel motors out last night and replaced the single bi-polar cap on the internal connector PCB of each motor. Found I had the takeup motor put together a little incorrectly...didn't have the concave thrust washers installed in the nose cap correctly. They should make an hourglass shape. This goes for probably just about any Teac/Tascam reel motor in this era...there is a flat brass thrust washer that goes in the tail cap, and two slightly conical black thrust washers that go in the nose cap...you put the tops of the "cones" together to make that flattened hourglass shape and that's how they go into the nose cap so there is constant pressure on the shaft bearings holding it axially in place firmly. If they are in wrong the motor operates fine but is noisy. Also noticed that the slots in between the commutator pads were a little packed with brush dust so I cleaned that up. Again, I've said this somewhere in the past, but it is worthwhile to make note of the orientation of the brushes when you take them out. If you put one back in upside down it has to "break-in" to the new position which decrease conductivity until it is worn to the new position, and that wear packs conductive residue in the commutator slots which also effects efficiency. Just put the thing back together the way it came apart. I believe I hadn't learned that when I last took this motor apart which is why it is already dirty inside and why the nose thrust washers were in wrong. You too can easily service your own reel motors, even replace the bearings.

Here is a picture of the back of the 58 at present. It looks like a horrible mess but it is actually coming along nicely.

 

[cjacek]

Cory, how do you keep track what goes where when it's time to put it all together? Do you take more photos, label things or? Real nice progress for sure.

 

[sweetbeats]

i have a parts deck...

Actually, in most cases I just remember, and when I'm concerned I won't be able to remember, like for instance the Control PCB...there's like 12 or 14 connections on that and many are the same size connector with all pins loaded so I labeled those...that goes for the Interface PCB too. The rest of it goes back together pretty logically. The IN/OUT PCB might look like a nightmare, but the cable lengths dictate which plugs connect in front and which ones hook up in back, and fortunately there are red and white jacks for red and white plugs, and furthermore the channels go from 8 ~ 1 L ~ R (viewed from the back) and you can see which color of wire goes to which jack on the jack panel so you know which section on the IN/OUT PCB PCB it hooks into (i.e. channel 8 has grey wires coming from the XLR and RCA jacks, they go on the first row from the left on the IN/OUT PCB because that is channel 8, and further more ins are one color and outs are the other color...red and white...and wires coming from the RCA jacks are two-pin and the XLR's 3-pin so it is pretty logical).

When I pulled the channel strip in the M-___ I ttok lots of pictures but I also checked first to see that all the channel strips' PCB's were interconnected the same way. They were so I knew I could just look at another channel strip to reference how it all goes back together...now I also have the wiring diagram I drew up...the master section from the M-___ is another story...LOTS of pictures cause its the only one I've got...maybe the only one anywhere and there are no diagrams or schematics......and lots of funky makeshift connections too.

Plus I do take pictures as I pull stuff apart. Sometimes I have to take a peek. Worst case scenario I do have the parts deck to reference, but there is no reason I'd have to have that...its a crutch that I know is there if needed and if I didn't have it I would probably be just fine with what I have documented/noted. BUT...you can never be too careful...wear your glasses and have good light and double and triple check things or you might just install an amp card on the extender board offset by one pin and pfffft!

 

[cjacek]

Cory, thanks for the extensive reply.

 

[sweetbeats]

bit-o-progress

The IN-OUT PCB (the balanced I/O PCB) recap job is now completed (there were 6 caps on backorder) as is the Control PCB (there was 1 cap backordered on that one). I have most of the caps on-hand now for the Capstan Servo PCB recap job but there are 2 oddball caps that are on backorder until late July. That is really what holds this whole thing up. The 58 is still all opened up and the Capstan Servo PCB has to go back in before anything else so it sits in a cool dark dry place and I'll get back to it in a couple months I suppose.

Just lettin' y'all know its still there and on the docket.

 

[mastercontrolme]

What oddball caps are you missing?