Tascam 244 - Non-functional inputs & panning problems

[MrNegative]

Hello all, new to this forum.
I picked up a very dirty Tascam 244 a couple months back and have since replaced the belts to get the tape mechanism working again. Upon testing the inputs, I found that no sound would come out at all. Nothing in my headphones and no activity on the VU meters.

Further testing revealed that I could plug an audio source into the receive RCA jack on the back in order to get some audio, but it only works on two of the tracks:
Track 1 - no input, no sound through rcv jack
Track 2 - no input, rcv jack operational
Track 3 - no input, rcv jack operational
Track 4 - no input, no sound through rcv jack

Oh, and panning the track fully to the right cuts the track completely.

Anybody have any pointers or directions for fixing this strange problem? I've pored over the block and signal diagrams and I can't figure out how the rcv jack works but the input jack does not. It's a really strange issue that seems like it may have a very simple fix, but I have no idea what it could be.

Thanks for reading.

 

[sweetbeats]

Step 1: connect your source to each input and see if you have signal at the SEND jack of each. Report your results.

Step 2: disconnect the 244 from power, jet some contact cleaner such as DeoxIT D5 down into the INPUT select toggle switches, exercise them (rapidly switch them back and forth maybe 50 times), do another flushing jet of contact cleaner, set the 244 on a rag with the front raised up for maybe 24 hours, then reconnect to power and test. You may need to exercise the switches again.

 

[MrNegative]

Step 1: connect your source to each input and see if you have signal at the SEND jack of each. Report your results.

Step 2: disconnect the 244 from power, jet some contact cleaner such as DeoxIT D5 down into the INPUT select toggle switches, exercise them (rapidly switch them back and forth maybe 50 times), do another flushing jet of contact cleaner, set the 244 on a rag with the front raised up for maybe 24 hours, then reconnect to power and test. You may need to exercise the switches again.

Thanks for the tips sweetbeats!

Here's what I found:
Track 1 - no send or receive
Track 2 - no send, only receive
Track 3 - send and receive, completely working
Track 4 - no send or receive

Regarding the switches, I gave all channel strips a healthy DeoxITizing outside of the machine a couple months ago, so I don't think that could be the problem. The components in the strips seem to be pretty resilient, so I'm surprised at the lack of consistency over what works and what does not across all four inputs.

Also, some additional info - Heads have been cleaned and demagnetized. No fuses in my 244 (US ver.). Rec & PB are perfectly fine. Also, nothing happens to the VU meters in the dead channels 1 & 4. Oh yeah, and the right buss is dead too.

Overall, I'm not looking for someone to do the heavy lifting for me with repairing my 244 - I'm just looking for some pointers towards common areas of failure/potential sources of my problems. Not a lot of info out there concerning channel issues, especially ones where receive works but send does not.

 

[MrNegative]

Just tried working with the right buss a bit - turns out I can get some sound if I crank the trim all the way - although it is still far more attenuated than the left buss and setting the input to tape still makes any playback inaudible.

 

[sweetbeats]

Don’t get hung up on why some things work and others don’t. Each channel is an individual assembly. Clearly your 244 was not cared for or maintained. It may have even been abused.

Also, you’re really hung up on why send doesn’t work and receive works…look at the block diagram. The input goes to the input amp and trim control. Then it goes to the send jack, and then the receive jack inputs the return and on to the rest of the channel strip. If the receive jack works as an input yay, the rest of the strip is good. If you get no signal at the send jack then either there is a problem with the input jack, wiring from the jack to the input PCB, problem with the source select switch, the input amp, wiring to the send jack, or the send jack itself. It could be any of these things. But the point is on that channel you’ve narrowed it down to something g between the input jack and the send jack. I suggested exercising the toggle switches because that is a common area of trouble, especially if the unit got really dirty, was not appropriately stored…if there’s dirt and it was stored in a humid environment the switch contacts could be corroded to the point you’ll ever struggle to make reliable contact and they need to be replaced. But the 244 is nice because you can pull the bottom cover off and get to pretty much the whole channel strip and start tracing where the signal drops off. You can also exercise connections inside. Again, if it was in a humid environment the co facts in the internal mini Molex connectors could be oxidized/corroded. They need to be exercised. You mentioned you treated the outside of the controls with DeoxIT. I’m not exactly sure what you mean, but, for instance, for the toggle switches you have to stick the straw down in the switch and give a good jet, then exercise it. Rapid flip-flip-flip back and forth maybe 50 times…maybe more. Then straw down in the switch and jet again. You can’t expect it to work if you just spray a little and leave it at that. Also what DeoxIT are you using? D5? F5? The switches require D5 which is for metal to metal contacts. The pots and faders use F5 which is for carbon element potentiometers, but you have to open the unit up to do anything with the pots. Spraying the shaft on the exterior will do nothing, and in fact can do more harm than good if lubricant is dissolved and leaks down into the body of the pot where the wiper and element are.

And if you can get some signal in the R buss when you manipulate the trim pot, that could be a blown opamp, bad solder joint…again, you have to trace it out and find where the signal drops. My assessment of your unit based on your description of its condition and operation tells me it was neglected and will need to be gone through and cleaned and inspected, and may have bad solder joints, failed active components, etc.

But confirm what you actually did with the DeoxIT and what kind of DeoxIT you have. Also try taking the bottom cover off and exercising any connection you can unplug and plug back in. Don’t be a gorilla with it…you an damage solder joints by muscling it. Study how the connectors come apart to make it easier to get them apart.

 

[MrNegative]

You mentioned you treated the outside of the controls with DeoxIT. I’m not exactly sure what you mean, but, for instance, for the toggle switches you have to stick the straw down in the switch and give a good jet, then exercise it.

Oops! To clarify, by "outside of the machine" I meant that I uninstalled each strip and was able to spray D5 directly into each pot. I've got all of the nonfunctional strips out again as I'm going to tear down each of the faders (according to one of your videos). Thanks for your advice and I'll get back to working on it real soon.