Tascam 246 VU Meter Issue

Level Anything

Level Anything

Member
Hey all!

First off, I haven't been coming around for a couple years and it's good to be back. Glad to see some familiar names still posting and helping people (shout out to Sweetbeats, famous beagle, cjacek)

So, to my problem... For the last year or so I have been working around an issue with my 246. The VU meter on channel one dies. I do a lot of transfers of sessions from the 246 to my DAW and I'll hit play and see all the tracks receiving signal in the DAW and their corresponding meters jumping, except for track 01. If I rewind to the very beginning (really from anywhere but I go to the beginning as to not accidentally record over anything), arm track one, and then very quickly hit REC/PLAY, the meter springs to life and then works correctly for a bit before dying again. So it's not completely broken but doesn't work like it should. It's especially annoying when I'm recording using channel one and can't see my levels.

I cannot figure out why arming the track and recording for a split second would make the meter work again but if anyone has any clue I would happily listen. Guesses welcome ;)
 
Do you have a link to a schematic? I can only guess there is a relay contact that carries signal to the meter drive amp and it has a dirty or weak contact. I also wonder if the relays are of the PCB type we used to see in Hitachi VHS machines? About the size of small lady's little finger tip, the contacts would tarnish because the recorder was rarely used to record. We used to cheat as getting them out was such a bind. Used drill a 1mm hole in the case and squirt in some Electrolube.

If signal switching is done by FETs or bipolar transistors these are historically problematic in all sorts of kit. Or, could be a decoupler on a DC switching rail.

The above should keep you busy while you contemplate how easy DAW recording is!

Dave.
 
The meters are driven by op amps that are NJM4560 and then go into diodes and capacitors for smoothing of the signal- Meters only display one polarity DC signals that represent the AC level. Looking at the schematic I have on the computer you problem can be a Tape/ Program switch or even before that IC U102 is a well known trouble maker in a lot of equipment which they call a Bilateral switch or CD4066. These are FET's that are switch on and off by voltages going to the gates- they are C mos type IC's and easily damaged and have a higher than normal failure rate. Of course you need to send in a 1KHz sine wave and scope out what is happening- If the Op Amp U101 continues to have the sine wave when the meter fails then I would replace electrolytics after the op amp. If the op amp loses its signal I check the input and then work the Tape/ Program switch to make sure this is not causing the problem. Checking the output line of the U102 (CD4066) they can call it other names too like NJM4066 but it is the same, see if the signal is staying on the output. It can even be a bad control line to the control input. This is all from a Technicians point of view and I have not seen this kind of problem in all my years but as time goes on more Electrolytics will fail and also there can be defective solder joints contributing to this loss of signal. So there is a lot to check but this is what I have to deal with- You could socket the board where the 4066 is and just try another one as well. They are not that costly and the 4966 a higher grade part might work there too.
 
There’s also an M5218 buffer amp after the 4560 meter driver. The M5218 part is on the actual meter amp PCB.
 
You must log in or register to reply here.
Back
Top