Have I killed my 424?

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fendermike

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Last night, while prepping for a new project, I cleaned and demagged my 424's heads (the original, tan model, not the MKII or III).

Like a dummy, and because I forget since it's been so long, I turned the tool on while it was in close proximity to the heads. I demagged as normal (I didn't realize my mistake right away). The resulting first track of the new recording sounds terrible and I get very low level on playback according to the meter.

Does anyone know if I've just temporarily magnetized the heads or if another pass done properly might solve the problem? I can't wait to get home from work today and poke around this some more. I hope it's not done for.
 
It's very possible that it's gone to that big gig in the sky.:(
 
Nice.

I'll let you know what I find later tonight. I don't want to have to start shopping for a replacement right now.

Anyone else with some encouraging reports?
 
Well, I demagged a few more times and now I have a few questions for those of you who may know more than I.

1) What is a normal level of dropoff from record to playback?
In other words, I record and peak at about +4db, but on playback, I'm only at 0db.

2)If playback of earlier recorded tapes is still good, can I revert to my "bad tape" theory to explain why a new recording is suspect?
Again, in more other words, is the record and playback head one and the same?

I think yes to the very last question, but would appreciate any confirmation.
 
Yes- cubed.

-Yes, the record and reproduce head is the same head, on the Portastudio.

-Yes, recording at +4 and getting +0 on playback is an average amount of disparity, relatively to a deck of that age, and probably indicates a slight maladjustment of the record/reproduce circuitry, which occurs over time.

-Yes, a bad tape could cause this problem with the rolloff of levels.

=======

The tape should be verified, as well as the cleanliness of the head, but beyond that, the level rolloff could be a minor adjustment problem. This would be common for a deck the relative age of the 424.

It's hard to say if any of these symptoms are from the demagnetizer being switched on near the head, but in general, this is not good. By the book, switching of the demag wand shouldn't be done near the head, 'cause it may blast magnetism onto the heads that can't be demag'd off. That's by the book, but YMMV.
 
Re: Yes- cubed.

A Reel Person said:
-The tape should be verified, as well as the cleanliness of the head, but beyond that, the level rolloff could be a minor adjustment problem. This would be common for a deck the relative age of the 424.
Click to expand...

Thanks. Are we talking about aizimuth? Is this user adjustable, or is bench testing equipment a pre-requisite?
 
Azimuth is part of the full alignment procedure.

If you're using the tape only on one machine, your own Portastudio, azimuth is important, but you wouldn't necessarily notice if azimuth was off, a minor amount.

On the other hand, if your azimuth is severly out of alignment, it could definitely affect one or more tracks, such as an edge track, like 1 or 4, and cause the problem you're seeing.

In general, problems with azimuth would affect you most if you used one tape in multiple tape machines. The azimuth on each machine would have to be perfect, otherwise you'd get a noticeable rolloff effect when you'd switch the tape between machines.

The mismatch in record/repro levels I was referring to, besides azimuth, I think has to do with balancing the gain stages in the record/repro circuits, and that's separate from azimuth, specifically, but they're both part of a proper alignment, by the book.

Just by my experience, I've seen older decks experience a bit of a roloff, betweed record and reproduce levels, that can be adjusted back into spec, by a tech or DIY'er. The adjustment I'm referring to is in the service manual.

BTW, Tascam still sells service manuals for most of it's products, last time I checked. If you're a DIY'er, the service manual's worth having. Tascam Parts is at (323) 727-4840.

If you're not a DIY'er, then Tascam Service is recommended. See www.tascam.com for all the details.

A bit of a minor rolloff may be annoying, but some of it can be compensated for on the input side. You'd just drive the input signal a little hotter when recording to the weak track. However, there's an upper limit to how hot you can go, before incurring distortion on the input side, so just experiment a little, and use your best judgement.

Any recorder with a severe mismatch in levels, or rolloff, that can't be compensated for by the user, is a good candidate for proper alignment and calibration by Tascam, or a capable DIY tech with the proper tools & a manual.

There are several maintenance procedures, of balancing levels in the signal chain, on any Portastudio or analog recorder, that IMO need to be done, from time to time, over the years. Most of these older decks experiencing rolloff in levels, can be adjusted up to perform like new, if the tech takes enough time and careful effort to align it properly.
 
Thanks for the detailed reply. It all makes sense. I have a service man who could perform the adjustment/setup for me.

Since I'll be borrowing a deck from someone to use while mine is of questionable status, I think I'll take it in for at least an estimate.

I don't think the heads are permanently magnetized, as I first feared.

Your reply is detailed and coherent, and I just want to say that such a thing seems rare these days on the net in general.

Thanks again.
 
Thanx Mike.

I guess I'm the unusual DIY'er who buys old Tascam decks with the intention of refurbishing them, and buys the Tascam service manuals and actually reads them.

I've adjusted and repaired a few Tascams in my time, and sometimes I try to pass along a few tech tips, hopefully without sounding too much like a textbook. Haha.

I also have a professional background in computer technology & repair, with 20 years of field experience, so taking things apart, poking around, and putting them back together is something I'm really good at, in fact, it's my specialty. These days, everything in computers is micro-miniaturized, but in the old days,... a tech really had to be a tech! Haha, do I sound old?

Scope alignments, test & measurement used to be all a part of normal computer repair, way back in the day, but now those things are a thing of the past. The first 1/2" tape drives I ever aligned were 9-track DATA tape drives, but the tech skills I learned transferred well to the audio-analog-reel tape drives, and analog based systems, like the Portastudio.

Anyway, the bulk of the problems & symptoms you'd read about on the HR Tascam forum, or Tascambbs, would break down into basically two categories:

1) the electro-mechanical problems related to worn out belts, grommets and pinch rollers.

2) the electronic-adjustment problems of gain/level adjustment and balancing of the record/reproduce circuits.

Azimuth is head alignment, which is lumped in with an overall alignment/adjustment procedure.

Very occasionally, you might read about someone who's burned out his Portastudio's input stage on one channel, by inserting a really hot source, and driving it all the way up, for "warmth". Haha. Sometimes if the input signal's driven hot enough, extrememly hot, instead of "warmth", you get "smoke"./DA
 
Oh yeah, BTW

The 3rd type of problem you might read about on the HR Tascam forum or Tascambbs, is the reel-to-reel deck who's reels wobble.

In this case, either the hub clamps are worn out, or the reel motor shafts are slightly bent, more than likely from having been dropped, i.e., the "UPS Syndrome".;)/DA
 
Thanks again.

I have a line on an 8 track, 1/2" tape unit for 600 dollars after professional refurb. I'm extremely interested. Don't know the details or even the brand yet since the deck is not in the shop yet.
 
1/2" 8 track is a nice, fun, punchy sounding format, a 'real' production format.

You're probably looking at a Tascam 38 or TSR8, which are both great machines. The 38 is VU meter style, and the TSR8 is the LED style w/built in dbx. Have fun recording & good luck./DA
 
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