Double Super HELP.... I Screwed UP !

D

Darkshark

Diamond Rio Monitors
I was replacing the lamps on my VU meters on my Tascam M-30 console....... with no problems..... until I decided to try switching the desk on before I buttoned it up to see if everything was cool. Things came on and then went off and never returned. The power transformer was very hot I turned it off and let it cool down. It has not came on since. Any ideas to try? Or do y'all think I cooked my power supply transformer?:(

I am super bummed.

DS
 
You probably didn't fry the xformer, but if it was really hot, that may indicate too much current was being demanded of it, which could have been caused by a short somewhere. Obvious question but have you checked fuses? Make sure there aren't any shorts anywhere. I don't have a schematic (and I'm not really a tech I just play one on TV...) but it is possible you burned out a part of the power supply as well, I don't know how complicated a PSU it is, but you could check for shorts there as well (with the power disconnected.)
 
I can't find any fuses. Power appears to go from the power switch to the transformer, to a quick disconnect on a small PSU board.... I see no fuses anywhere. I turned it back on and with a VOM could see no voltage coming out of the transformer. VOM set to 20 VDC black probe to ground and red probe to each contact coming into the quick disconnet attached to the board. I wish I could find a fuse.

DS
 
a question

I don't mean to be rude or presumptuous, but are you knowledgeable and skilled in electronics? If not, you not only are unlikely to fix this, but could cause more damage, and even hurt yourself (fatally).

If you are, just check (I've made this mistake) - is the VOM set for AC volts? You'll see zero at the transformer output if it's set to DC.

That said, I'd perform a really good visual and sniff check - is anything burnt? How does the transformer smell? Any burnt components?

By the way, fuses can look like axially leaded components, soldered into PCB's

Do you have the schematic? Don't proceed without the schematic.
 
I am not very skilled in electronic trouble shooting. I see nothing burnt. I do have the schematics for the desk.........I will try a different setting on the VOM... I set the VOM to DC because of all of the LEDs and DC lamps are behind the transformer...... I will probe the inputs to the PCB/PSU board on AC setting just to test the condition of the transformer.... that is about all I am comfortable doing on my own.

Thanks
 
Seek professional help

  • I would leave it alone. It is surprisingly easy to electrocute yourself.
  • think of what you will do with any debug information you get - if the transformer output is apparently O.K., then what?
  • can you send the schematics?
 
I went as far as I was comfortable. I tested each pin coming from the transformer.

No voltage at all on any setting AC/DC on the VOM....

DS
 
There was a grounding lug going to the frame on the PS board....... that is where I put the black probe. There was 6 conductors in a quick disconnect... I probed each one with no results.......maybe I was in error.

The really bad news is that tascam has discontinued that transformer, if it is indeed that...... I may cut my losses and sell the desk to someone more adept or who maybe needs parts and channel strips.

Thank you for all of your suggestions.

Tony
 
You're welcome

Don't panic. It might not be cooked. Could be something simple and cheap.

The way you measured might not show an voltage, if the output if the transformer is floated, which could be.

Can you send the schematic? Or, take the board to a technician.

Good luck.
 
Got it...

O.K., let's go back to the beginning. Did you replace al of the bulbs? Did you use exact replacements? If not, what were they? Did you disconnect, change or touch anything else? How much of this did you have to take apart to get to the lamps?
 
OK.... I used these bulbs.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=070-275

I also tested with LEDs (with 130ohm resistor in line) which worked well also, but I went with the lamps.

I did it with power disconnected. Before I used some alligator test clips to clip the new lamps to the terminals the old burned out ones were hooked to. Powered on and the news ones lit. I tried all of the terminals...... that is when the alligator clip test hookup lamps went out..... and I noticed the transformer very hot. I turned everything off.... disconnected the power and replaced the lamps. I took the console apart more then was needed.... but I didn't know that at the time. I tool the bottom off..... then loosen the back to get to the screws holding the meter assembly... I took that off and was able to get to the meters..... everything seemed fine.

That is pretty much what I done..... nothing seems burned anywhere, I never smelled anything.

That is all I could remember doing.

DS
 
more...

Darkshark said:
I tried all of the terminals...... that is when the alligator clip test hookup lamps went out..... and I noticed the transformer very hot.
Click to expand...

Can you be more specific about this part of the experience?

Also, how do you know that those bulbs are the correct replacement? Did you match up specs or part numbers?

It may be possible that the 4 bulbs you put in ended up being too little resistance, and you drew more current that the transformer could stand, and burned out that winding on the transformer.

Disconnect P1 and with no power (i.e., unplugged), measure the resistance of each secondary winding: red-red (P1-1,2), org-org (P1-3,4), blue-blue (P1-5,6). Use a low Ohm range, this should be pretty low resistance.
 
Darkshark said:
I used the information I found in this post for the lamps I used.
https://homerecording.com/bbs/showthread.php?p=3163713#post3163713

Is P2 gonna be a pinned quick disconnect... that I would just pull away from the Power Supply Board?


DS
Click to expand...

Yea, I read that post earlier. Can't go by that.

I don't know about P2, but it's shown as a connector on the schematic. It might be vertical pins soldered to the board with a receptacle housing pushed over it, but I don't know. Take a pic and send it.
 
Check the transformer...

...as I mentioned before, the resistance of the secondary windings. You might need a transformer. Also, those bulbs might have done it, so might want to get the specification for the OEM bulb, or get some bulbs (call Tascam).
 
OK, Thank You !..... since I did call Tascam, not about the lamps but about the transformer... it has been discontinued for the M-30......This was a hobby project.....it might be best if I part out this console or get it to someone that might need a spare for parts. I have an M-208 which works fine just sitting in the floor that I am not using as well.
 
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