Channel 1 on 388 Repro at Half Volume

R

rorohello

Member
So...never had a single issue with my 388...until I moved it across country and back.

Now the first channel repros at about half volume compared to the other tracks.

Is this an alignment issue? It was in a storage space up on its side for a while.
 
Tape path clean? Like surgical room clean? It takes VERY little debris on the R/P headstack to significantly reduce or entirely eliminate signal flow to a track or tracks.

Did you change tape? I’m assuming you are reproducing tape previously recorded on your 388 and reproduced with no issue, so I assume the answer is “no”, but I want to ask anyway because there is an issue that often arises with edge tracks when switching to non-Ampex/Quantegy tape from those brands. I can explain more if you like or if this is the case.

Did you try reseating your cards in the cardbay, particularly the dbx and amp cards? Or did you try swapping amp cards to see if the problem follows the card or stays with the track?

Is the problem also present when monitoring playback from the respective TAPE OUT jack or is it only when monitoring through the mixer section?
 
Hello again Sweetbeats! Appreciate how active you are here. Very valuable resource for this community.


sweetbeats said:
Tape path clean? Like surgical room clean? It takes VERY little debris on the R/P headstack to significantly reduce or entirely eliminate signal flow to a track or tracks.

So when I first noticed it, I cleaned the crap out of everything. There was certainly dirt coming away and this DID bring the level back up a bit, but not to full former glory. Yesterday I cleaned everything again as best as I could to test this theory. Still same trouble. When recording a vocal track on channel 1, signal is loud and clear while tracking with the Mon in my headphones, and then plays back at about half the vol of the other tracks

Did you change tape? I’m assuming you are reproducing tape previously recorded on your 388 and reproduced with no issue, so I assume the answer is “no”, but I want to ask anyway because there is an issue that often arises with edge tracks when switching to non-Ampex/Quantegy tape from those brands. I can explain more if you like or if this is the case.

Yes. I use to always use Ampex 456. But switched to RMG SM911 recently. All the other channels seem to think this tape works fine

Did you try reseating your cards in the cardbay, particularly the dbx and amp cards? Or did you try swapping amp cards to see if the problem follows the card or stays with the track?

No. I'd be a little scared.

Is the problem also present when monitoring playback from the respective TAPE OUT jack or is it only when monitoring through the mixer section?
Click to expand...

Great point. I will see
 
Okay...so you switched from 456 to SM911. That *may* be your issue. Try this...when you are playing back a reel of SM911 that has program material on track 1 that you *know* has a good level to tape, but the playback signal is weak, ever so gently, while you are playing back the tape, with your finger or a pencil or whatever lift the tape away from the face of the machine...place whatever you are using to lift the tape right before the record/reproduce head...in other words apply some light upward pressure on the edge of the tape like you are lifting the tape toward the ceiling, but just gentle pressure. Does this help the signal?

The deal is, Ampex/Quantegy did not have as accurate a tape slitting operation as other companies...there was greater variance in the width of their tape...I'm talking only 0.001~0.003", but that was enough that, to avoid tape possibly being slit too wide they slit the tape a little more narrow so that if the slitting ran wide the tape would still be within the specified maximum width for whatever format tape they were slitting. What this means is that if the machine has had a long history of running Ampex/Quantegy tape, and the wear groove on the head was worn by the more narrow tape, when you put tape on that is slit to a more exacting standard like the SM911, it'll tend to lift just slightly at one or both edge tracks as the tape edge runs up against the edge of the wear groove on the head. I'm not making this up. I had the same issue and talked with folks that have been involved in the industry decades before I used any of this stuff. 3M tape, AGFA/EMTEC/BASF/RMGI/RTM was all slit on more exacting slitters.

Try it out.

And regarding you feeling a little scared about re-seating your amp cards, get over it. :D Seriously though, you want to get comfortable re-seating/swapping amp cards. They are meant to come out. I and others here can give you pointers to help make it easier, but this may be a very important diagnostic step if my advice above doesn't help.

So...keep us posted.
 
Hey Sweetbeat. Tried the lifting up and it certainly didn't bring Channel 1 clearer. Sort of hard to know whether I'm doing it right however. I'll try testing the Tape Outs later. I have to dig up some RCAs to 1/4 for this.

I feel like maybe this is something I live with. What is the Rx if this tape width thing is the issue?
 
rorohello said:
Hey Sweetbeat. Tried the lifting up and it certainly didn't bring Channel 1 clearer. Sort of hard to know whether I'm doing it right however. I'll try testing the Tape Outs later. I have to dig up some RCAs to 1/4 for this.

I feel like maybe this is something I live with. What is the Rx if this tape width thing is the issue?
Click to expand...

Try gently guiding the tape closer to the face of the machine also. I'm pretty sure track 1 is at the bottom of the headstack, but those heads are mounted upside-down so-to-speak...track 1 should still be at the bottom, but try nudging the tape down instead of up to see if that makes a difference.

Depending on the depth of the wear pattern on the face of the R/P head the solution could be as simple as FFWD & REW over an entire reel of tape several times with the lifters defeated, or if wear is significant the only solution is to have the head relapped. Can you put up some pics of your R/P head? Use a bright flashlight and get in as close as you can without losing focus?

Did this problem start immediately the first time you started using the RMGI tape, or have you had successful operation with the RMGI tape but then suddenly this problem arose after you had been using the new tape for a time? Maybe you've already made that clear and I apologize for asking if you have, but its an important question. In my experience, of you have trouble related to switching tape brands like this the problem arises that first time you are using non-Ampex/Quantegy tape. So I suspect your problem may not be this issue if you were using the RMGI tape for awhile.

I know you said you cleaned the heads, but if you have a significant wear groove on the R/P head you really have to be diligent about cleaning up the edges of the wear path. Cotton swabs won't do it because they are relatively firm and all roundy like, and can't clean out the corners of the wear path. Get some good quality 100% cottom makeup remover pads; the pads make it easier to get in there to the nooks and crannies. Make sure you are using at *least* 91% isopropyl alcohol or a cleaner specific to cleaning tape machine heads.

If nudging the tape doesn't have any effect there's no reason you should have to just live with this. I'll be interested what you discover when you monitor from the TAPE OUT jack, and beyond that swapping amp cards is such a quick and easy diagnostic tool to narrow the source of a problem down on a macro level.
 
Record on all tracks.Flip the tape over so that trk 1 plays back on trk 8. Does the problem follow the recorded track-8 plays back OK-or does track 1 still playback @ 50%? this will show you if the problem is on the record side or the playback side.
 
Thanks guys. Ill try all this stuff later after work.
[MENTION=79692]sweetbeats[/MENTION] - no reason not to just go ahead and do the FFWD RWD before a more diligent cleaning with the pads?
 
Yes there is a reason. Always start with cleaning. No sense in submitting the tape path and tape to unnecessary wear if the R/P head just needs more thorough cleaning. Wkrbee’s suggestion is a good quick too. This will narrow down if the issue is happening st the recording and/or playback stage and could rule out a tape-to-head contact issue and lead us in a more pertinent direction.
 
Hi Guys,

I'm in the studio today, but the main goal is too complete acoustic treatment. Still, I took some photos of the R/P head (I think) with the flashlight

Dropbox - IMG_20181110_145110.jpg

Dropbox - IMG_20181110_145033.jpg

I also tested and confirmed the signal comes out weak from the RCA Tape Out on the back.

Please let me know what my next steps should be. I'm guessing the tape flip?

Also, I have the reference test tone tape if that helps at all in diagnosing.
 
Yeah do the tape flip.

That’s a moderately worn head there, but the wear looks pretty even. Try the tape flip and then the next thing I would do is swap amp cards and see if the problem follows the card.
 
Hey y'all. The tape flip made Track 8 play weak and 1 play strong. Which is a good thing correct?

I'm now into the card seating/swapping territory?

There is also a burned out bulb on one of the VUs I'd like to sort out if I'm going to be opening her up.

Thanks all
 
So the tape flip means there is an issue at the recording stage, it’s not an issue with your head and it’s wear path and the type of tape you are using. So, yes, you want to remove the cardbay cover and swap the card that includes track 1 with another card and see if the problem follows the card when you record and reproduce.

Replacing VU meter lamps is a much more invasive procedure on a 388 than swapping amp cards...like partial disassembly of a good portion of the chassis. It’s a pain. Let’s start with the amp card swap.

[EDIT]

Yes, you would think it would be as easy as replacing a light bulb in your house to swap out a meter lamp, but noooooo...you have to detach the meter bridge housing enough from the main chassis so you can tip it forward to access the screws that hold the meters to the housing and worm them out, and since they are hardwired to each other in pairs you pretty much have to remove all or at least most of them in order to be able get the pair that includes the meter with burned out lamp out far enough so you can get the lense off, desolder the old lamp and solder in a new one.
 
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I don’t think you need a whole thread. The cards plug in. Do you have the manual? There is a page with a picture of all the cards in the cardbay and labels as to which cards are what. The amp cards are on the left...IIRC the dbx cards are the back row, then two rows of amp cards (two tracks per card), and then the shorter cards in the front are he meter amp and balance amp boards. Pinch the corners of an amp card between your thumb and index fingers, one corner per hand, test your wrists on the top of the meter bridge so you have some controlled leverage, and sort of rock back and forth pulling a little harder on the left, then the right, then left, etc. it should pop out. They are usually a little stubborn at first, but they’ll come out. Remember, they are designed to unplug and come out for servicing. Give it a shot.
 
The tape skewing in and out of the worn groove during the record process could cause it to appear to be on the record side. Is the low output a solid level or is it fluctuating?
The pictures you posted show that the head is badly worn, guides and tape lifters are worn. All will cause tape edge damage. A re-lapping is in order-but the head may be too worn. Guides can be rotated but the lifters may be a problem.
 
The VU meter bulbs can be replaced by pulling the DBX cards and some of the R/P cards. Unscrew the meter assy You can then pull the meter assy up out of the unit and change the bulbs.
 
You'll want to reach out to JRF to get a quote.

Yes you send the entire headblock assembly to JRF including the block, erase head, R/P head, guides, etc.

But do the card swap first.
 
The card swap is a good idea-any way to further isolate the problem will save you money. If you are going to go the re-lap route,be aware after you get the heads back,the 388 will need a complete recal. It includes tape tension adjustments,head alignment,playback alignment with a playback alignment tape, setting up all the bias and playback traps,(because the head inductance changes when the head is re-lapped),re-biasing for the type of tape you use, record level, and crosstalk adjustments. You may as well have the capstan belt replaced,and a pinch roller if you don't have a good one. Don't scrimp if the problem is head wear.
 
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