tascam 58-OB part Deux

[evm1024]

To begin our story you need to go back to the beginning in this thread:

https://homerecording.com/bbs/showthread.php?t=262192

I'll need to sit down and read through all 18 pages just to be sure that I get it all.

As you may know I picked up Sweetbeats Tascam 58. It has a few problems but much potential.

I've been a bit crowded in the garage<<<< er, Studio with too many decks and not enough space. I need to finish off a Pininfirinna Spider Europa project and a few others as well. But to make things go better I built a 32" x 8' workbench. This will allow space for the 58, the DX4 recap/calibrate and the 32 and atr100 and Hardy M1 DIY and GR mp2 and , and , and.

Anyway, I did get the bench up and have the 58 there. I was able to get the power supply working. I had to dig around for a while to find a 7805 regulator in a parts box along with a 7815 and some transistors. I was able to scavenge some parts off the parts 58 that made it all work. There was a problem with the +|5 v logic supply that was traced to a faulty replacement 7805...

I'll post some photos as things get more interesting.

The take home message here is that I pulled the fuses that supplied the power supply board and then brought up each rail individually. Fixing the rails as I went. So pull the fuses, select a rail or pair of rails to work on (I started with the +5 logic rail) and unsolder the wires taking the rail to the deck. That isolates the supply rail until you have it working.

Once a rail is up and clean resolder the PS to deck supply wires and power up listening for "something bad".

The end results is a working PS and no smoke. The controls do not work yet. If you hit play it starts the take up reel moving backwards and then stops. But this is progress.

--Ethan

PS I must really give lots of credit to Cory. He put this machine back together and made videos of doing so. It looks like it was never apart with no missing screws and everything dresses nicely. This speaks to the degree of organization that he brings to his DIY projects.

 

[cjacek]

Ah, yes, the fascinating and sometimes sad "story" continues indeed... Cory's 58 went to a good home. Thanks for keeping us updated, Ethan.

 

[dodgeaspen]

I almost like the looks of the 58 more then my 38. What are all the switches in the front used for? Sorry, I've never seen a 58 close up. It looks like it has many more features then the 38, hence the higher number.

 

[sweetbeats]

Its...its...its like my baby is all grown up and I've just gotten a phone call from him...heheh...unh...that was weird.

Thanks for taking it on, Ethan. I'm excited for what you've done already, and hopeful for continued success but that story remains yet to be told.

 

[evm1024]

lightly

I'll post "lightly" about bring this deck up to functional condition. It will come in spurts and runs. I've got about 6 hours into it so far to get this far. But all is looking good. The capstan does not spin but I expect to get that in the next round. Then when the transport is running we tackle the audio....

Regards, Ethan

 

[sweetbeats]

Yeah...I don't expect to get "calls" often nor for them to be long. Just nice to see it and I look forward to tuning in next time there is info. Just really appreciate you continuing the story.

 

[evm1024]

After a long weekend....

I got a bit more time into the deck. Lots of things were fixed and I'll only post about the more interesting ones. All in all about 15 parts were replaced so far.

First the PS was brought up rail by rail. Then each subsystem was connected. Then the capstan motor control was fixed. Then the reel motors were tested and some basic servo alighment was done.

I was really puzzled with the take up reel. All was wired correctly and things were just not working as expected. Then on the threshold of a dream last night I realized that the motor was running backwards. I studied the schematic and nothing would allow this as designed. I checked the wiring again and all was well there. This leaves a few possibilities but being a PM DC motor and being a pragmatic person I just reversed the leads to the motor.... The end results is shown in this 8 MB video http://studio.arafel.org/tascam-58/Tascam-58-transport-test.wmv

No audio cards yet, no servo calibration, tape rubs across the reels and who knows what else. But this is progress.

Regards, Ethan

 

[sweetbeats]

YEAH BABY WOO-HOOOOOOOOO!!!

Oh MAN all I can do is giddily chuckle watching that video!! HAHAHAAAA! WOO!

You're freaky smart, Ethan!

Okay...so when you get to it I'm really curious what all has required replacement so far.

I really can't figure out the motor going backwards...did I get the leads on wrong on a joint PCB? No...you said the wiring was correct. Hmmm...I wonder...There's a little PCB inside the motor with a BP cap on it...did I...I may have replaced the lead on one of those as it was either too short, or damaged...unh...can't remember but THAT may be why it was spinning backwards, and that was all done after I cooked it the first time so that would add up. Yeah...I might've installed the leads backwards on that...

Ethan, I'm watching the tension arm behavior. I had always wondered if the recapping would take care of the old issue with tape tensions and the arms DO appear to be behaving more normally...the main thing I'm looking for is to see that the tension arm closest to whatever reel is supplying tape in fast-wind mode drops down to more like a 6 o'clock positioin after the reel motors reach stable speed. The left side was always the problem one in FFWD but it is looking better. Definitely will need to check the tensions though, but it is looking great!

I betcha the tape is rubbing on the reels because the tension arms and reel tables are set for thick-flange precision reels. Is the tape rubbing on the top flanges?

Aw man this is cool and I'm glad for your sake too that it (so far) is coming together.

Congrats!

 

[evm1024]

progress

Just an update on this deck.

Channel 8 was kinda messed up for playback so I was able to do some work on the channel card and then I was able to calibrate it to a 250 nWb/m tape. Both sync and repro caled up +-2 dB except at 32 Hz which is normal. Just a quick cal.

Moving over to a record cal I found that - it did not record. All the record LED armed and enabled as one would expect. But it remained in playback which is actually good news. This indicates that part of the cmos logic on the control board is toast. Might not be too hard to locate.

So the plan is to get record working then do some upgrades on it. Bias cap upgrade so that it can bias GP9 and 499 and ATR. Replace the relays on the channel cards. Upgrade the opamps to something like the LME49860 and a few select EQ caps.

Then calibrate it for +6 and bias to one of those tapes. Might be nice to mod the master bias so that one could switch between different bias levels.

--Ethan

 

[evm1024]

New Update

I got some time to work on this deck again today. It now records but has not been calibrated yet.

All channels did not record but did playback. I poked around looking for logic errors that would mis trigger the relays and such. It all looked good. Scratching my head a bit it dawned on me that to record you need the bias signal.

With the scope I was able to prove that there was no bias. Off to the master osc board and no signal there. Quickly swapping in a spare the problem remains.

So, pull all the channel cards and power up and the Master Osc is working.

One or more channel cards is pulling the master osc down.

It turns out that channel 8's card is the reason. Of course given that this was the card that was mis-inserted. Another oddity is that the master osc was running at 125 kHz and should have been 145 kHz. A quick adjustment and the osc is on freq.

To make the long story short I farted around with channel 8 card for a bit then just swapped in a spare that I had. I needed to install a few caps that were not in my spare.

Right now all channels playback and record. I think that tomorrow I'll swap in the bias coupling cap mod and do a full calibration and see what we have here.

The mod will allow biasing a +9 tape. The deck is normally biased +6. I'll stay at +6 for now but who knows.

--Ethan

 

[The Great Cobb]

too good

You are too good at fixing things.

 

[evm1024]

You are too good at fixing things.

Don't count your chickens yet. Still have to get it cal'd up.

THnaks, EThan

 

[sweetbeats]

Nope...

I'm with Cobb. You're too good at fixing things. You are providing technical redemption for my carelessness at inserting channel 8 incorrectly.

Off to count the chickens now.

Chicken #1...
Chicken #2...
Chicken #3...
Chicken #4...
Chicken #5..............................

 

[evm1024]

Success

Well now - Just finished up calibrating this deck. I think we can declare victory. Calibrated to +6/185, Biased to 499. Records +-3 dB from 40 Hz to 24 kHz. (those are the -3 dB points) -4 dB at 35 Hz. 2 dB headbump at about 150 Hz.

The only remaining problem is that some of the relays appear dirty (ch 3,5 and 6) and can read low until bumped. I had planned on replacing the relays anyway.

I used a 220 pF Wima cap for the bias feed. This is actually too much as that with the 220 it just can adjust the bias low enough to find the peak with 499/GP9/996. THis means that it will not find the peak with 456 so you would have to overbias by ear.

The stock feed cap is 100 pF - So when I replace the relays I'll put a 180 pF in there and rebias.

Regards Ethan

 

[sweetbeats]

That...is...AWESOME!

Ethan, this is pure closure to a chapter in my life and I thank you. Yes the 58 is entirely your property but I guess in my mind I hadn't let go of the responsibility for damaging it...now I can. Ready for service and those response specs are...impressive!

A champ is that 58.

The relays...recall that those were problematic and I've already opened them up once and cleaned them knowing that it was a temporary fix at best, and considering it has been a couple years since then with very little use you are certainly right to choose replacement which, in hindsight, would have been good to do way back when but at the time I wasn't confident in my ability to desolder the stock relays.

So, in a sense the Tascam 58-OB Story is finis.

Time to load it in the CS-607 and track drums, huh?

 

[evm1024]

Good weekend for working on things

THe 58 is in the roll around rack and I thought I needed a little more to go with it. So I cut up some rack mout rails that I had lying around and drilled and tapped some mounting holes in the roll around. Thus I have 6U or more rack space about the deck.

I've put a Presonus M80 8 channel preamp (Jensen, OPA627) and a Tascam M1B. This lets you record up to 8 tracks and monitor on headphones.

Regards, Ethan

 

[sweetbeats]

Truly good to see progress on this, Ethan.

I've seen a riser kit for the rack I have my BR-20T in...wish I could still get one. I think it adds 8U above similar to what you have done there.

Any subjective or objective audio tests with this mobile unit?

 

[evm1024]

Truly good to see progress on this, Ethan.

I've seen a riser kit for the rack I have my BR-20T in...wish I could still get one. I think it adds 8U above similar to what you have done there.

Any subjective or objective audio tests with this mobile unit?

This riser is adjustable. Currently set for 6U but could go to 8U or 9U.

The 58 is an outstanding deck. I really fell for it once I got I got it going. My 38 will be sold as well as my MS-16. The 58 will cover all my tracking needs. I'm mostly a 2 track direct stereo recordist anyway. And the MS-16 takes up too much space.

I've not got any "real" tracking done on it yet. I'm setting it up for a remote recording session with a guitar player I know who wants to play all the parts as well as sing along. This is where the M1B comes in.


Regards, Ethan

 

[courtneyblush]

What an amazing job

One of those style racks is the next thing I need, do you have any spare cosmetic parts from a 58-ob?

 

[sweetbeats]

Is that question to me or to evm1024?

I don't have an ounce of 58 stuff anymore. Used to have a complete parts machine and everything but sold all of it.