Tascam 388 Channel 1 level issues on playback

[JeromeyRome]

Hi, repairing my Tascam 388 and am stuck on this one spot. When I record on to channel 1, the playback is crackling and fluctuating in levels. When I plug an input into both line and mic on channel 1, the signal passes through all outputs fine, and the meter shows a stable tone when I play a 440hz tone through for monitoring, but when I record that signal to tape and play it back the sound is messed up. This is showing up on the channel meter and L/R stereo output meter, and the issue is printed onto the tape as I’ve recorded from input one then flipped tape and played back on channel 8, where the issue still resides.

I’ve swapped both the channel PCB cards and rec/rep cards in the back to test, and the issue does not reside in either those locations. I checked the MAS. BUSS PCB and cleaned it, all seems fine there as well. Tape head has been cleaned. Head does show some wear, but the tape looks to be making good connection. Can anyone help?

 

[sweetbeats]

When you say you swapped R/P amp cards and the “issue does not reside” there, are you saying the problem doesn’t follow the card swap? I’m pretty sure that’s what you are saying but I want to verify.

Is there anything else you’ve done to the machine recently? Like did the problem start after servicing the machine in some way, or after an incident moving the unit or anything? Or did the issue just spontaneously start one day?

When is the last time you demagnetized the heads and tape path? That’s a bit of a reach there is a possible cause, but I want rule it out.

What kind of tape are you using? Does the problem occur with any tape you put on the machine and with different tape types?

Can you post some good pics of the R/P head?

Have you re-seated the bias cards?

 

[JeromeyRome]

When you say you swapped R/P amp cards and the “issue does not reside” there, are you saying the problem doesn’t follow the card swap? I’m pretty sure that’s what you are saying but I want to verify.

Is there anything else you’ve done to the machine recently? Like did the problem start after servicing the machine in some way, or after an incident moving the unit or anything? Or did the issue just spontaneously start one day?

When is the last time you demagnetized the heads and tape path? That’s a bit of a reach there is a possible cause, but I want rule it out.

What kind of tape are you using? Does the problem occur with any tape you put on the machine and with different tape types?

Can you post some good pics of the R/P head?

Have you re-seated the bias cards?

Hey thanks so much for your response. The problem correct, the problem does not follow the channel amp cards.

I just got the machine and went in to fix channel 8 which wasn’t making sound, then after I fixed channel 8 I notice the problem happening on 1, could have been there the whole time I’m not sure.

I have never damagnetized the heads and tape path but will try to do that and get back to you. I’ll try some other tape I have as well, and will also post pics of the heads.

I will also try to reseat the bias cards, which ones are those?

 

[sweetbeats]

I thought the issue was tracks 5 & 8. It’s between 1 & 8? What kind of tape are you using? How long have you had this machine?

And as far as the bias cards look on page 1-26 of the Maintenance section of your Operation Maintenance manual. There’s a picture of the exposed cardbay with the different cards labeled.

 

[JeromeyRome]

I thought the issue was tracks 5 & 8. It’s between 1 & 8? What kind of tape are you using? How long have you had this machine?

And as far as the bias cards look on page 1-26 of the Maintenance section of your Operation Maintenance manual. There’s a picture of the exposed cardbay with the different cards labeled.

No, the issue right now is only track 1. The rest of the channels are totally fine. Track 8 had a connector unplugged which was an easy fix. I’ve only had it for about a week and have mostly just been testing and cleaning it. I honestly don’t know what kind of tape it is it was just a reel that came with the machine. Which tape would you recommend I use for it?

 

[sweetbeats]

Can you post a couple good pics of the R/P head?

Do you have any known tape to choose from, or is it all just mystery tape?

While recording to track 1, gently apply some upward pressure on the edge of the tape closest to the machine at the intake side of the headblock assembly. What I’m wondering here is if your wear path was formed by Ampex/Quantegy tape, which was purposely slit slightly undersize because of accuracy issues with their slitting equipment. So they undersized in order to avoid at all costs the tape being too wide. That means tape paths worn by such tape tend to be 0.001”~0.003” more narrow than the standard, and when you put tape from a non-Ampex/Quantegy manufacturer on the machine one edge, either track 1 or track 3 tends to lift slightly…brought to loose signal. You can test by gently and slightly applying some upward pressure for track 1 to see if you can record signal. Usually you’ll comprise track 8 to get track 1. But this at least helps us know what’s going on.

 

[JeromeyRome]

Can you post a couple good pics of the R/P head?

Do you have any known tape to choose from, or is it all just mystery tape?

While recording to track 1, gently apply some upward pressure on the edge of the tape closest to the machine at the intake side of the headblock assembly. What I’m wondering here is if your wear path was formed by Ampex/Quantegy tape, which was purposely slit slightly undersize because of accuracy issues with their slitting equipment. So they undersized in order to avoid at all costs the tape being too wide. That means tape paths worn by such tape tend to be 0.001”~0.003” more narrow than the standard, and when you put tape from a non-Ampex/Quantegy manufacturer on the machine one edge, either track 1 or track 3 tends to lift slightly…brought to loose signal. You can test by gently and slightly applying some upward pressure for track 1 to see if you can record signal. Usually you’ll comprise track 8 to get track 1. But this at least helps us know what’s going on.

Hey sorry about the delayed response, got busy before I could test again. So I put a different roll of tape on that I have, still don’t know exact what it is, and I applied pressure upwards on the tape as it ran across the head and the issue is still happening. To be more specific about the sound, it’s a crackling and popping noise along with the recorded signal, with some fluctuations in volume. I’ve uploaded some photos of the R/P head below.

 

[JeromeyRome]

Can you post a couple good pics of the R/P head?

Do you have any known tape to choose from, or is it all just mystery tape?

While recording to track 1, gently apply some upward pressure on the edge of the tape closest to the machine at the intake side of the headblock assembly. What I’m wondering here is if your wear path was formed by Ampex/Quantegy tape, which was purposely slit slightly undersize because of accuracy issues with their slitting equipment. So they undersized in order to avoid at all costs the tape being too wide. That means tape paths worn by such tape tend to be 0.001”~0.003” more narrow than the standard, and when you put tape from a non-Ampex/Quantegy manufacturer on the machine one edge, either track 1 or track 3 tends to lift slightly…brought to loose signal. You can test by gently and slightly applying some upward pressure for track 1 to see if you can record signal. Usually you’ll comprise track 8 to get track 1. But this at least helps us know what’s going on.

Hey just wanted to follow up and see if you had any other ideas, really appreciate the help!

 

[sweetbeats]

Did you ever demagnetize the heads and tape path?