Tascam 388 Story...

sweetbeats

Reel deep thoughts...
Oh I think I actually remember that error...forget color and just go with wherever the ODD PGM master fader is plugged into.

Leave the fader connected for the first two tests. You can unplug the yellow connector from the BUSS A PCB for the third test and probe the sockets on the connector.
 

Vicshat

New member
I'm about 90% confident I'm doing this correctly. I have my mulitmeter set to "2" sensitivity.

When I check between 7 & 9 on the white connector I get a reading of .251

When I check between 8 & 9 I get .003-.004

Between 5 & 9 of the yellow connector I get .085

I counted pins according to the schematic and counted "1" as being the white pin furthest from the red EVEN connector. I'm pretty sure that's right. When I start counting from the other direction (1 being closest to the EVEN connector) I get no reading from what would be 7&9 or 8&9.
 

sweetbeats

Reel deep thoughts...
Okay let's stop for a moment and regroup.

1. You said "schematic" in your last paragraph. Are you talking about the picture of the PCB in the manual?

2. The connectors are labeled with a "1" at one end by pin #1. Locate that mark and verify you were measuring the correct pins.
 

Vicshat

New member
I was looking at diagram 4-6 (buss B PCB) in the schematic diagram section.

I see the "1" marking now and my process was correct. When I tried again just now I got

.249 between 7-9
.011 between 8-9
.134 between 5-9 (yellow)

I did change the input gain a little from last night when I was double checking the PGM assignment just now.
 

sweetbeats

Reel deep thoughts...
Okay.

Do that same set of tests except assign tone to PGM 1 and measure AC volts between:

• pins 1 & 3 on the white connector
• pins 2 & 3 on the white connector
• pins 1 & 9 on the yellow connector
 

sweetbeats

Reel deep thoughts...
Without changing anything can you measure AC volts at the PGM 1 output jack? It should be about the same as what you just measured between pins 1 & 9 of the yellow connector.
 

Vicshat

New member
When I first tested it was jumping around a lot between .085 and .250 but it settled at .167

No reading from pgm 5 out.
 

sweetbeats

Reel deep thoughts...
Don't jump ahead. I'm having to assume you assigned tone to PGM 5, and you probably did, but I don't know that for sure and false assumptions is how we get lost and start chasing our tails. It takes a lot more time to troubleshoot through a forum and for not not being able to be at the machine and actually see what you are doing. So, please, as asinine as it may seem, let's just take it step by step so I can confirm what's being done.

So now assign tone to PGM 5, measure again between pins 5 & 9 of the yellow connector, and then also at the PGM 5 output jack.
 

sweetbeats

Reel deep thoughts...
Leaving all test conditions the same (i.e. tone assigned to PGM 5), find connector P109 on the BUSS B PCB. This is the connector that goes between the board and the PGM out jacks. Measure AC volts between pins 5 & 9 on P109.
 

sweetbeats

Reel deep thoughts...
I originally presumed you had a bad fader booster amp (the triangle that comes after the fader in the block diagram...U381 on the BUSS B PCB), or a bad component or faulty trace or solder joint associated with that amp because it feeds both the PGM out jack as well as the PGM signal to tape, and you have a problem with both of those. I'm not certain yet, but I think there may be two separate issues, one each associated with your two problem areas. This is why we take things step by step because you never know when your problem might have more than one cause.

The testing we have been doing is to affirm signal is getting to the fader (measuring between pins 7 & 9 on the fader connector), and then checking to see if signal is coming out of the fader (measuring between pins 8 & 9...this signal level is bound to be much lower than coming in...this is the nature of an audio resistor which is what a fader is and why there is an amp on the back side of it to boost the signal back to nominal level), and then seeing if the amp is outputting signal (pins 5 & 9 of the yellow connector J111).

To be sure we compared results to a known good path (I picked PGM 1). Things seemed normal. So I had you measure at the output jacks (which is the other side of the output path from the fader booster amp U381). As expected, PGM 5 is nil. So I had you back up to where the jacks connect to the BUSS B PCB and you've got signal there.

Look at the schematic when you read through my explanation above so you can follow along. The schematic only shows detail for PGM 1 amplifiers because the rest are the same, just different component numbers, so use PGM 1 as your example.

So let's start with what is likely to be a more simple problem and deal with the output jack. You need to set your meter to continuity and measure point to point from pin 5 of P109 to pin 5 of J109 (the connector), and then keep going (one probe stays on pin 5 of J109) until you no longer have continuity. I don't have a 388 so I can't guide you better than that but just connect the dots. My assumption is the wires from P109 go to a PCB to which the jacks are mounted. Just trace it out. I suspect you have a bad solder joint. I'll try and explain further if this doesn't make sense.
 

Vicshat

New member
I might have discovered one problem early in the chain.

To test the continuity I set my meter appropriately and I touched one terminal to the solder lead for 5 on one side of the PCB and the other terminal to "top" of the connector where there are little slots. I was not seeing any change on the meter so I thought I might be missing something in the process. I checked against PGM 1 and 3 was immediately getting a reading and a beep. I check the J109 connector and the spot for 5 does not look like the others. The metal inside the connector is not angled like the others, it's almost flat against the plastic part so the pin on the PCB side is not able to make the connection. Should I attempt to push that back in gently?
 

Vicshat

New member
Well, gently isn't doing it. I don't know that it's possible to push through from the outside to straighten that metal strip. At least I know where the problem lies so I can find a solution.

I was planning to use it for some recording tomorrow so I just got it put back together and now something strange is happening with playback. When I listen back through the monitor section everything is normal. When I listen through the LR assignment through the mixer the tracks are not playing back on the correct channel. Material recorded to track 6 is playing back on 5 and material recorded on 4 is playing back on 3. I was feeling pretty good about the progress today (again, thank you!) and then this... so it goes.

The input selector and EQ section are still working correctly, i.e. material recorded back on track 6 only plays back when 6 is set to RMX. The EQ for material on track 6 is affected by channel 6 EQ.

The volume fader, pan, and eff send for material recorded on track 6 are all on channel 5 of the mixer.

I was very careful when poking around in there earlier but it seems I've still managed to get something out of whack.
 

sweetbeats

Reel deep thoughts...
The only decent way to deal with deformed contacts in those RCA jacks is to remove the jack set and get to the contact from the side of the jack. I don't know if that makes sense. The alternative here is to use a set from your spare unit. THIS is where swapping parts or assemblies makes sense...when you've identified the problem and can choose to repair, or if it is easier or repair isn't possible, to swap the part/assembly.

Regarding your other issues...wow.

Stop and retrace your steps. There really isn't anything in the mixer logic you could mess up that would cause these kinds of issues. It sounds like a misaligned connector. What connections did you disconnect and reconnect? Look at the guys and make a list of them, and the carefully examine those connections to make sure they are proper. I can't emphasize how important it is to take great care when mating connectors to make sure they are properly aligned and appropriately placed. Generally if you screw up an audio connection the results aren't catastrophic. If you mess up a connection that carries power and grounding, the results can be permanent. I severely messed up a mint condition model 58 1/2" 8-track once because I had a rec/play amp card offset by one pin...took out a couple of the power rails and cooked some logic circuitry. I could begin to fix it.

I'm not sure how you could have done that with the way the connections are in the 388 so I'm not accusing you of being careless, but we need to start somewhere so let's go over what you touched and make sure it is properly reconnected.
 

Vicshat

New member
I got careless when hooking up the send rcv snake to the patchbay and got a couple crossed and got things all confused. Annoying and embarrassing mistake but at least an easy fix. :facepalm:

On the connector problem... to be clear it's not the RCA jack that I have a problem with, it's the plastic wire harness connector that connects to the PCB. It looks as though the other end of the harness is soldered right onto the rca jack board. It might come down to swapping that harness, maybe easier to replace the harness and rca jacks instead of resoldering.
 

sweetbeats

Reel deep thoughts...
I LOVE it when a crazy problem turns out to be something simple like that! :guitar:

Yay!!

Can you possibly post a pic of what you're talking about then with the connector problem? I'm not getting it, and I thinks it's just because it's been too long since I've been into the guts of a 388 I can't picture what's going on.
 

Vicshat

New member
Yes, I'll get a pic tomorrow but I can be more clear.

It's the slot in J109 that receives pin 5 from P109. The metal piece inside the hole is bent or possibly broken so pin 5 has nothing with which to make contact.
 
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