388 dropouts on first track

J

Janah_f

New member
This isn’t my first 388, but it is my first run in with the type of issue I’m experiencing. When I picked this unit up, all of the cards needed to be reseated, some of the input selector switches needed to be cleaned, heads were a bit gunky, but with even and shallow wear. All simple stuff!

I was still having trouble without occasional dropouts, distorted audio and HF loss on channel one. I should note, playback on channel one is just fine. This only happens when I’m printing to tape, and it doesn’t matter which input I use, or how it’s routed.

So, I did a lot of troubleshooting, and it seemed like getting the take up tension within spec and increasing the record bias for channel 1 worked okay to solve my distortion and HF loss problem.. however I’m still getting some detectable dropouts, and overall unpleasantness. I’m using brand new tape, and it does the same thing with the other reels I have.

Not quite sure where to go from here. The head does look to be in good shape, and great sounding playback on other prerecorded tapes sort of eliminates that possibility. Would love to hear if anyone’s got some ideas :)
 
Thanks! I’m using LPR35, but this happens with any reel of tape I use. It’s also worth mentioning that I swapped out the bias cards and the channel cards, and the problem is still present on channel 1.. So the rec/repro and bias PCB are not suspect. I’m really at a (HF) loss here! ;)
 
The symptoms you describe and the troubleshooting you’ve executed point to the problem being at the rec/play head. You say it happens with “any reel of tape.” List in detail what tapes you have tried that exhibit the problem.
 
Hey sweetbeats. I appreciate your responses/expertise.

I'm thinking this may be a head related issue as well. I have only a few reels of tape. A couple of older scotch tapes (non sticky shedding formulas) that have pre-recorded music on them, that play back just fine (all tracks, including track 1) However, recording to the scotch tapes or the brand new reel of LPR35 results in the dropouts on track 1. I have determined with certainty that the dropouts/HF loss/distortion occur while recording only. Here's an additional list of things I've done to further troubleshoot:

1. demagnetized the rec/play head and tape path (this may be worth another, more aggressive attempt)
2. thoroughly cleaned entire tape path
3. adjusting alignment of rec/play head (some negligible improvement)
4. recorded material on track 2 and physically moved the tape during playback so track 2 would reproduce on track one of the play head, which proved these artifacts occur only during rec.
5. removed headstack to closely examine condition of heads. no visible issues.
6. run a reel of LPR35 in fast wind mode with the lifters defeated a couple of times
7. applied gentle pressure to the tape while recording in an attempt to make better contact with the head during rec (hard to determine the effectiveness of this)

So, I suppose to question I would like to find an answer to is what would cause a single head design like this (which uses same head for rec/repro) to print with artifacts but playback just fine?
 
If the dropouts only happen on the channel one then it could be the head height has been altered and that the M300 jig should be used to verify that the head is in the right place. I hear all kinds of guys on forums say they inprove the sound by ear by turning the screws on the head- they don't even know what they are doing but most likely making a mess of their deck. On the ones I work on here it is clearly visible of the inaccuracy of their adjustments. Also realize that the edge tracks are prone in any format to have more irregularities than tracks 2 to 7. I have seen this and it is well known over the years. What make it worse is when dealing with cassette width track on a reel tape the technology is pushed to the limit and issue are going to present as more and much more maintenance will be needed. Is the Pinch roller in pristine condition or dirty? This can affect the tape path and create skew which a mirror tape would show. The Mirror tape is the MTT902.
I worked at Teac in the 80's and at the shop that bough the Chicago Factory service location for 10 years more. I was a Lead Technician when I was at Teac in Chicago. I now run my own business doing this same work but unfortunately the 388 is just too large for any of my benches.

On larger format tape where irregular tape to head contact is observed, I have found that polishing the head surface with Nu Finish Car polish- the stuff in the orange bottle helps the head contact and also applies a surfactant that act as a lubricant to lessen head wear. I have seen 1dB variation in levels at 1KHz go down to 1/2 of the value when after the polish job. This might help your situation maybe.
Also consider the relay that may be in the record path- I have had relays in the TSR8 go bad and tapping the card when in record would cause level changes. The relays are old and sometimes need to be replaced.
 
My new poly pinch roller from Athan arrived today, and I installed it. I also got a bottle of “Nu Finish” and polished the head a couple of times, and I noticed a big improvement on track one. I didn’t have a great deal of time today, but I did record a minute or so of audio onto track one and heard no drop outs. It has been rather intermittent though, so it’s hard to say. I will do more testing tomorrow!
 
I appreciate a number of things Skywave had to offer, and glad you seem to be getting some results with those suggestions. They support what I was asking about as far as the tape types you tried...all those tape types you mentioned have more accurate slitting width than Ampex/Quantegy tape. The slitting equipment for Ampex/Quantegy tape wasn’t as precise as other brands, so what they did is purposely under-sized the tape width. We are talking only a couple-three thousands of an inch, but they did this because they knew their slitting accuracy wasn’t good enough and couldn’t risk tape running *over* the standard and not fitting inside tape guides etc. So what this means is, since the 388 head does not have edge slots cut into it, if the tape wear pattern is generated by Ampex/Quantegy tape and then you put a tape type such as Scotch/3M/BASF/EMTEC/RMGI or other tape (which has much more accurate slitting standards), often the tape will ride or curl at one of the edges and it takes almost *nothing* of this to mess with the performance of either track 1 or track 8...usually track 1 on the 388. That’s probably part or all of your issue.

You mentioned in your post a couple posts ago you “adjusted” the r/p head...man, I wouldn’t mess with that. The height is fixed and unless you have the proper height gauge like Skywave mentions you are risking a lot messing with that, and you *do not* want to mess with the wrap angle that has been established already. If there is a wear pattern established, you want to leave the guides and the head alone, unless you are having the head relapped. And if you are doing that then you send it out to some place like JRF and rotate the guides and let John set the wrap angle.

I had this problem on one of my 388s, and the solution that solved it was a relap. That eradicated a wear pattern I can only assume was established by Ampex/Quantegy tape, and I was using LPR35...track 1 problems. I could get better performance by gently applying some upward pressure on the tape at the r/p head, but then track 8 suffered. This was the action that sort of confirmed the issue for me. After the relap I had no issues.
 
I know head adjustment without proper tools is asking for trouble, but my thought was “I am taking this in for a relap/examination anyway, what’s there to lose”. The adjustments I made were very minor, but did improve tape to head contact... almost a guarantee that if it is used in this state for any length of time an uneven wear pattern will develop.

I would like to consider this problem solved for the time being. Running the tape with the lifters defeated and the polish worked wonders. No dropouts or HF loss to speak of on track 1 or 8. I think you are right about the quantegy/ampex tape screwing with the wear pattern, sweet beats. Sticky shed all over when I picked up this machine which is indicative of use of those tapes.

Happy to have at least tracked down the source of this issue, even if a relap is in the near future. I only paid $500 for this machine, and cosmetically it is mint. (Sold as non functioning bc capstan belt had become useless. So I think that’s an overall net win for a 388 in 2020...
 
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