TASCAM DA 60 MK2 battery-buffer (CR 2430-FT10) discharge in 3 months

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Pispotti

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Mantova - Italy
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TASCAM DA60 MK2
Hello everyone.
I bought a used dat DA 60 MK2 that works very well but has a problem with the buffer battery welded to the Control PCB: any new lithium battery I tried to install (CR 2430 Renata, Varta, Duracell) does not last more than three months ! Thinking of some strange dispersion (caused by some tiny solder particles stuck on the tracks) I thoroughly "washed" the Control PCB with isopropyl alcohol and a soft bristle brush, but without success. Now I don't know what to do: if I put in another new battery in three months, at most, I will have to change it (I've already done it 5 times) and if I don't put anything on, the machine remains set to the factory settings every time it is switched on. Has anyone, by any chance, had the same problem? Where could the leakage current be and how should I go about finding and eliminating it? Thank you all.
 
Look for any electrolytic caps in parallel or even a ceramic. Something is discharging that battery that otherwise lasts a much longer time.
 
Thank you SkywaveTDR. Are the capacitors you're referring to all on the Control PCB or can they be elsewhere too?
 
I don't even work on these but in general any cap that is around and in the memory- battery circuit should be checked or if Electrolytic replaced. I have had Monolithic caps take AM Radio stations off the air due to shorting- Monolithic means ceramic. Use a Polystyrene or Polyester cap and it will be much less leakage. In the V900X which uses a super cap for memory retention I upgraded the .1F to a .47F cap. There are caps out there that are even much larger than .47F and some I have see than are 4F is size at 5.5V. Wrkbe is the expert on Digital type decks.
 
Great Skywave tip! I re-extracted the Control PCB and around the positive pole of the buffer battery there are no capacitors but two diodes D1NS4 F4070 (40V - 1A). One of these, with a welded battery, caused the diode tester to sound: broken.
 
Good. The DA88 I was putting a battery in of that same type I remember putting a socket on so they could be changed easier as otherwise you need to take a significant amount of parts out to get to the battery.
 
Yeah, great idea. If even changing the diode the battery still runs out I will take out the buffer with a two-place 1.5 V AA battery holder (at least when I change them I don't have to extract the PCB every time).
 
Well there are things that have changed that it is draining the battery. Jim Finch would maybe have greater experience due to the Factory Service position he held. We saw only a couple of the deck like that in Chicago and in the shop after Teac sold it. They did not come in as much as they were heavy to transport. Maybe there is a chip spec somewhere that would tell you what the drain would be to the battery. As silicon hardens with age it might mean it conducts more current at a point- I would be looking at what kind of current was drawn out of the battery. Yes you can hook up a gel battery with a 3 V regulator but that is going a bit far. There may be a more simple solution out there- after all the battery just usually hold a supply on a memory IC that needs to retain data- if it lasted years in the past then it should not be discharging fast now.
Jim's label is wkrbee.
 
Unfortunately, even this umpteenth CR2430 has discharged in a short time. The fault was not the diodes. Continuing to extract the card every 2 months to change the battery does not seem healthy for the slot and the card itself but also leaving the machine without battery forces me to set various parameters of the menu every time it is switched on (the standard ones are not all suitable for mine needs). Since, immediately after the purchase, I mounted a battery holder on the pcb (so you can more easily change the battery without having to unsolder / solder every time) if I put a new battery, could I identify the location of the leak with a tester?
 
I myself would hook in a well regulated power supply so that the battery would just be there for power outages. Too bad things are designed this way. There have been EEproms for a long time already and to make something that uses a battery is just the cheap way of doing it.
 
Have you checked the schematics? I found a service manual online with pictures of the PCBs. It's not the Mk2 and didn't include the schematics, but the PCB tracks and components are shown. The one I found was a bit fuzzy but it may be enough to trace the tracks and see what components are in parallel with the battery - the round item marked BT1 on page 43/44. There's a 6264 chip near it, which I believe is a static ram, so could be where the config settings are held and needs to be retained... I'd start round there.
 
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Jim had stated that in a DA78 they made a mod that increased a resistor from 1 Meg ohm to 10Mohm for this problem. It was in series with the battery to the chip. He does not have the manual due to his move that it is in storage. This is a possibility.
 
Looking at the DA-60 as suggested the 27C512 is a CMOS EEProm and the current draw is at 25mA and goes up to 75mA when active at full clock speed. I would think that 25mA for a small battery would be a lot. Depends on the Ah capacity of the battery. The CR2430 has a Ah rating of 320mA or .320 A so I would not think it would hold up for long. The question is why would voltage have to be maintained on a EEProm as they are suppose to hold data with no power applied.
Russ Bachmann at New Jersey Factory Service used to work on these in days past. We got very few units in Chicago in the 80-90's.
 
The ram is the chip above that one. You're right, there's no need to power the eeprom, but certainly the static ram. There's a larger capacitor C41 above the battery but the picture isn't clear enough to see if the battery track goes to this. Could be a good candidate for checking. There's also a resistor R39, which may be the 1M you mentioned, but again the trace isn't clear. Maybe pispotti can sketch the traces from the real pcb. The only other capacitor is the decoupling one for the ram chip (C30), so this could be checked for leakage, and the isolating diode from the battery may also be leaking in reverse. Can't tell which of the 4 diodes (on my diagram at least) is connected to the battery.
Update: here's a temporary link to the pcb photo.
 
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I would have to consult those who work on these all the time. Jim Finch was service manager at Teac in CA so he is likely to have inside info that most shops will not. If the increased the resistor from 1 M to 10 Meg in the DA78 changes are that is the same on the DA60.
 
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