Snagged a Tascam 58! Good and bad news...

J

jeancoltrane

New member
So after slugging it out with my teac 2340 for the past year I finally decided to grab an 8 track off kijiji. Good news, transport seems to be in great shape & the heads look good, all lights & functions work except...

1 channel is stuck in sync mode (knew about this when I bought it) due to the relay, which I've read is pretty common and a simple fix. My repair guy in toronto bought most of the remaining tascam parts (so I've heard) and has the relay in stock.

The bad news - either I didnt notice it when testing at the sellers house, or it happened during the move to my place -
There seems to be a fair amount of noise & hum (sounds like 60/120hz) on all channel outputs, only in repro mode when moving tape. Input mode is dead quiet. The noise also appears on sync mode when playing back the tape. I'm not technically inclined at all, so I will likely get my repair guy to deal with this when he fixes the relay. Just wondering if anyone has encountered this type of issue and if I'm looking at a simple fix or a potentially bigger issue.

The machine also came with a reel of rmg sm900, which it was apparently aligned for. I've read the stock 58s couldnt bias +9 tape without mods, so is it reasonable to assume mods were done to bias sm900 properly, or perhaps no mods were done and it was aligned as close as possible...is there a link or info out there on what the proper mods would be to bias for +9. Also if anyone knew where to grab a manual that would definitely help my process of troubleshooting this beast.

Thanks for any help
 
Hey there.

I've experienced something like that once on a BR-20. There was a pinched wire. It sounds like there is a shorting/grounding issue in reproduce mode whether the source is the sync or play head, which tells me it's not the heads, because the problem occurs regardless of the source. I would start with getting the relay fixed, and re-seat all the amp cards.

In stock trim the 58 bias amp cannot produce bias level adequate to bias +9 tape. I'll have to look for the posts that detail the mod. It is in a thread by evm1024 regarding his MS16 (which shares the same amp cards). There is a capacitor on each amp card you replace with a different value allowing the proper level. Once you have the info you can just look at your cards to see if the value of that cap is stock or modified.

Hope we can help get things sorted out and congrats. I've got a soft spot for the 58.
 
C42 on the amp cards is the bias coupling capacitor. Stock value is 100pF. Suggested modified value is 180pF which should allow proper bias for +9 tape, but still enable biasing +6 tape.
 
Thanks very much for the info sweetbeats! I'm going to pop the channel cards out today and take a look. At the sellers house he was swapping the cards around to show the sync issue followed the card & was most likely the relay, so its possible something got popped loose or a wire got pinched reassembling causing the grounding hum.

Thanks again :)

ps. this machine is way bigger and heavier than it looks on the internet, lol.
 
tascam58.jpg

Sorry for the lack of updates, was on a mini tour for the past weeks but finally got home and had some time with the 58! Some good news is that the hum issue I was having seemed to fix itself, or was possibly due to some issue with one of my mixers. But I hooked up my crappy behringer to it last night and ran some tests - wow! sounds awesome and super quiet. the electronics seem to have an abundance of headroom. I was running some mp3s to tape with the meter pegged the whole time and didnt notice any distortion except for sweet sweet tape saturation (on +9 even) My mixer was giving out before I could hit it any harder so it remains to be seen just how much headroom I have left, but very pleased so far.

One strange thing about my 58 is its RCA ins and outs only, not sure how common this was. But I remember reading a thread with Jim Williams where he suggests modding the RCA's to +4 somehow, and using those instead of the XLRs. Any thoughts on this?

Also I guess I'll be needing a decent mixer soon, was thinking about getting a newer mackie 16/4bus or something (dont really want to deal with older consoles that have problems, have a few of those already :)) My main concern is getting something with direct outs, I was wondering how common mixers with post fader direct outs are (if thats a thing) I want to be able to hit the tape as hard as possible, but not sure what db directs outs usually send at (-10, +4?) ie - If i want to hit the vu on the 58 at +3 but the mic pre/direct out clips before I can get it that high, I'd have to use the bus outputs or some such thing? I'm probably missing something obvious here but any advice is welcome! I plan to pick up some decent standalone pres and mainly use the mixer for monitoring.

Cheers!
 
The amp design on the 58 is pretty neat, but it is driven by fairly typical 15V bipolar power...headroom is limited by the amplitude of the power supply rail. The fact you have what seems like a lot of headroom is likely related to the way the 58 is currently setup...the meter, input and output levels to which it is calibrated. This is not to sound critical of the 58. I'm just saying you can setup a tape deck so that the meters read 0VU when the actual signal level is really hot, and at the same time have the input level pots on the amp cards dialed back so what actually hits tape is mild compared to the high output settings on your mixer or whatever is feeding the deck. It's all adjustable and who knows how your machine is setup. Maybe you do.

Have you calibrated the machine? And what kind of tape are you using?

Regarding RCA only jacks, there were two models, the 58-OU, and the 58-OB; "U" for unbalanced (-10dBv RCA interface), and "B" for balanced (the RCA interface and +4dbu balanced on XLRs). You would achieve nothing if you modified the 58 to have +4dbu unbalanced on RCAs. The 58's nominal internal level is -10dBv. To modify the I/O to be +4dbu you would simply be adding additional amplifier circuitry to match levels of your other gear, which is the ONLY reason I would do that mod, but otherwise you should be able to match the -10dBv nominal level of the 58 with your mixer. It doesn't get you any more headroom or shizzle or anything to have +4dbu...those are all just nominal level interface standards...the point is to have gear that inputs and outputs signal in the same nominal level range and most mixers easily handle and are designed around the -10dBv standard. I recommend you not worry about it. As far as using the RCAs instead of the XLRs (if you have the option) I DO recommend using the RCAs...the ONLY reason to use the XLRs is if you have noise issues in your studio that are abated by using balanced interconnects (this is typical if you have loooooong signal runs, which is why balanced audio was adopted by the audio industry from the telephone industry in the first place...to deal with noise interference...not because it sounded better...in fact it was a catch 22 because to abate the noise by balancing one has to send the audio through more amplification circuitry, and balancing and unbalancing circuitry...). But even on paper the 58 audio specs are better using the RCAs. Be at peace with them and reject the "noise" that says balanced is more better (pun intended).

Regarding your mixer options and the direct out levels and all that...lots of options. I prefer the older Tascam stuff to most of the new stuff, except for new stuff that is a bit more $$$. You'll have to look at whatever you are interested in as far as presence of direct outs and their nominal level, but all you need is unbalanced -10dBv. Not a tall order. Lots of mixers have that. And here again you are concerned about having hot output to "hit tape hard". Again, tell me what tape you are using, then we can talk about starting with a standard setup, and then modifying from there so your meters reflect 0VU when your levels hitting tape are at the desired "hotness". The big picture to understand here is you have control of the output levels from the mixer, and you ALSO have control of the input sensitivity at the tape deck (how "loud" that signal is to tape) and independent control of what the meters show relative to the actual level of the audio going to tape.

[EDIT] nevermind...I see you are using SM900. Are you using any noise reduction? Nice pic by the way. Warm and cozy.
 
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