Tascam 244 recording issues

[Levi]

I had recently got a tascam 244 and replaced all the rubber parts, the machine plays tapes but it doesn’t record them, I’m gonna tear down the whole thing. Is there a specific place I should be extra attentive with to resolve this issue?

 

[Levi]

On the dbx board there are resistors and transistors missing; however, it doesn’t look tampered with because there were tied cables above the dbx board and the pads don’t look like the were desoldered.

 

[SkywaveTDR]

For those that are not experienced Technicians in a unit the most common issue is the record enable switch either has a broken off wire or that it got positioned to where it does not work. Rather than trying to get into circuitry that is much more complex it is best to start at the simple stuff. Record enable switches are in upper left of cassette compartment.

 

[Levi]

Thank you, ill check that out tomorrow, do you know anything about the dbx board? I watched a video of someone removing the dbx and theirs was also missing some parts that are marked on the pcb; however, on tascam ninjas website the dbx board has those components. I’m assuming its due to my model being Japanese, any ideas?

 

[SkywaveTDR]

They make boards that could be used in other decks. For instance a Tascam 34B card will plug into a Tascam 38 but the circuits are missing to use it as they are different machines and have different layouts. You have to be careful what you plug in and replacement parts do not always work. I tell my trainees that board replacement is the last thing a Technician does as this is not how things are fixed. The question is does your dBx unit work? If it does then don't worry about part missing that are not needed. The one thing to be careful is that Japan units are 100Vac only so you can not use them in US at 120 or other places with 240Vac without the appropriate transformer. I have a Variac when I have to fix unit here in the Chicago area to lower voltage to 100Vac. They also sell transformer devices for this as well.

 

[Levi]

Yeah it works, I was just shooting in the dark as to what might cause the issue. I am also in the chicago area, what is your shop called?

 

[Levi]

What does the record enable switch look like? Is it next to the capstan motor?

 

[Levi]

The led stays solid when recording but no actual recording is made to the tape, so does that mean that the recording is enabled, but there is a fault somewhere?

 

[SkywaveTDR]

Yes, If it enters the mode and stays there then it can be a bad relay on the record card. I can remember taking the card out and finding these relays and like all relays they can go bad on you.
On the record amp board the relay is called K401 and it is at one of the edges. You may have to take he record amp board out to access it. A scope on the appropriate head wires when tested against a different channel can show you if the signal is the same or different. If the relay is bad then it will be a lot different. I have only had a couple go bad in 47 years so it is not a common thing. A lot of problem of every kind are caused by broken solder joints on a PCB. You should have seen the Tascam 3030 I am working on it is full of bad joints.

 

[SkywaveTDR]

To answer a previous question the shop is called Skywave Tape Deck Repair and I am located at the SW corner of O'Hare Airport near Rt19 and Rt83. I am so backed up right now I have about 180 units to work on.

 

[Levi]

What do you mean when you say a scope, an oscilloscope or a sinewave generator to trace the signal? Also where should i go for a suitable relay replacement? I haven’t got around to testing it or resoldering the board yet.

 

[Levi]

I aaw a video on how to test car relays, would it be the same? Energize it to see if it clicks and then check the resistance?

 

[Levi]

Also thank you so much for your help, I probably would have re soldered every board by now.

 

[SkywaveTDR]

Car relays may be a higher current version and you have to be careful of driver devices. The best way to test a relay is to remove it and turn it on with a set of 9V batteries. It will energize a 24V relay with 18-20Vdc. I use a Leader DC power supply on my benches. It is easier to test a relay by tapping on it when it is on. Then check the section of tape that it was tested over to see if any improvement was observed. The scope on the bias trap test points can also tell you if the bias is coming on as that is where it goes. The bias trap just keeps the bias from going back into the circuit that make the audio portion of the recorded. Of course if that signal is missing then that is the problem. Usually if erase for a channel is working then the bias is there too.
Testing a relay in circuit is bad because you may damage the transistor that turns it on with outside voltage. A DVM in diode test can tell you if the transistor has good or bad readings.