Tascam 246 Tape Head Stuck in Play/Record Position

[SwisherSweet]

I recently picked-up a Tascam 246. It was sold as fully serviced (levels, pots cleaned, the whole 9 yards..). I put a tape in the unit and the first thing is does it eat my tape. I managed to get the tape out, but now the Tascam 246 is stuck in Play/Restore position:



Note, the capstan starts turning immediately if I press the two tabs at the top that detect the presence of a tape, so I don't think this is a simple belt issue.

Pressing Stop does not cause the tape heads to relax. Only Pause allows them to come back. Any ideas that might be causing this?

Also, the headphone jacks in the 246 output a ton of white noise even without any sources being connected and all channels in the Off position. I own several Tascam recorders (644, 688) and don't hear any noise in them unless I pull up a channel's gain real high.

Thanks.

 

[skywaveTDR]

When a person sells something as serviced, you need to ask who did the service and most the time it is fraud and they just want your money. What kind of warranty did they offer as a serviced deck should have a warranty- mine is 6 months.

 

[TalismanRich]

One word...... REFUND!

Obviously it's not a "fully serviced" piece of equipment. Belts don't cause the logic controlled functions to go bonkers.

 

[SwisherSweet]

Thanks. I already have received a refund for this and am considering making the seller an offer as a parts/repair machine if it can be repaired. Seems you are suggesting the logic controller is damaged/defective. Sounds reasonable to me. Any recommendations on troubleshooting steps to help isolate this as the cause?

Also, the headphone jacks in the 246 output a ton of white noise even without any sources being connected and all channels in the Off position. I own several Tascam recorders (644, 688) and don't hear any noise in them unless I pull up a channel's gain real high. Is it normal for the 246 to have noticable white noise from the headphone jack?

 

[skywaveTDR]

OK, The problem you have is the cam system- either a belt or that the feedback pot is dirty. In all the years I have never had a logic problem on a Portastudio.

The headphones on some stuff is cheaped out as on a Tascam 122. What did they use? A speaker amp with 40dB of gain wide open and only allowed the input to be the limiting factor. This is cheap and fast but also noisy. The real solution is to get a headphone circuit out of a higher grade deck and incorporate that into the deck but I don't know if it would fit. I did some research on that subject for the 122 I moded but the real answer was a completely different circuit and I did not have time to have a board made.
I put in a couple of LM386 IC and it was quieter but not like the real high end stuff. Why not get a schematic of a RANE Headphone amp and copy that into the deck? I am sure Wheatstone also had headphone amps. One reason noise would be present is that an unstable condition exists and the amp is oscillating at some high frequency- you might just need a new chip or maybe someone put a BiFet op amp where a normal one was and did not bypass it correctly. They will oscillate and burn out of not done correctly.
A Tascam 52 headphone amp circuit was seen as a good design and one I would copy. Op Amps ae getting quieter all the time but when you have to provide power from them then you need a push pull like current amp circuit after the Op Amp. This is done with transistors. You only need about 250mW or maybe as high as 1/2 watt but no more.

 

[skywaveTDR]

I am sure I have had this kind of problem in the hundred or so that came in. I fixed them all and this is why you get made Lead Technician besides good numbers of production and few or no recalls (those units coming back). In some cam systems there is a part that links the pot to the cam gear. This part often broke as it was a thin nylon part which was called a joint. I had a number of stronger ones 3D printed up that are designed to be much stronger. The pot through a voltage tells the controller where it is. If the controller gets confused sometimes LED blink to say error or other models they just jam up and stop.