Tascam VL-A5 studio monitors blowing fuses

[Warren Daly]

I have a pair of VL-A5 monitors. Each speaker intermittently blows the recommended fuse 250v 2amp glass fuse. The input is stable and at a reasonable volume. The amp is at 50% volume.
I replaced the fuses and 1 will not power up. I've opened them up and there is nothing burned or black inside.
A volt meter seems to suggest the coil stepdown transformer after the main 250v input board is not receiving voltage.
The nearest service center is in another country. If I had schematics/service manual I might be able to investigate more.
Thoughts?

 

[chucklechops]

I'm in exactly the same boat. Blew the occasional fuse when I first got them but got more and more frequent to the point where one of them just blows as soon as I switch it on. Had a peak inside and couldn't see anything untoward; although my knowledge of electronics doesn't go beyond being able to solder.

I wonder how risky a higher rated fuse would be.

They are well out of warranty now and I've upgraded to some Yammys but it would be nice to have a second pair or sell them.

 

[Warren Daly]

Please do not insert a higher rated fuse.

Both of mine keep blowing fuses, but now 1 of the units will not power on after the fuse is replaced.
I opened both units, swapping the various boards and transformer around until I found out what the issue was. This torodial transformer has it's primary coils shorted out.

The main amplifier board is supplied by a white connector block, it has 2 black leads, and 2 red leads. The two red leads are 24.5V AC, the 2 black leads are 0V/Ground.
I actually replaced the entire transformer and bypassed the first circuit board (with the relay).

The new fused torodial transformer is giving out 25V AC out. So I connect it the amp board after removed the existing broken transformer. No I will run it to see if this unit will start to blow fuses.

 

[sakis]

Why internet has to be like that ???? Warren Daly you don't have a f**cking idea what are you talking about !!!
Tascam has a circuit that automatically will detect input voltage that will mean that connection for 120 or 240 volt will happen automatically
Skip the circuit rewire the trafo directly the transformer according to the voltage of your country and you are done
Nothing else

 

[Warren Daly]

My first piece of advice was not to insert a higher rated fuse. The specification is 2Amp. Do not insert a 2.5 or 3Amp fuse. This advice would apply to any electronic equipment. Inserting a higher rated fuse is not a good idea.

I have replaced the transformer, hardwiring for my country supply of 240VAC and stepping down to 25VAC. As per my previous post. The audio amplifier board needs 2 rails at 24.5VAC and 2 ground rails. This is a fact. As I have used a scope and meter on this white block connector to the audio amplifier board.

The torodial core was confirmed to be shorted. See previous post for a link to the picture.

My monitor is running perfectly again. My studio is back up and running (and is safe)

chucklechops contact me to discuss how to fix your monitors. (FYI I am a qualified electronic engineer and I like to share knowledge)

Best Regards
Warren

 

[Jarno]

Why internet has to be like that ???? Warren Daly you don't have a f**cking idea what are you talking about !!!

Please keep your anger under control. This is place for civilized discussion. Not for personal attacks.

 

[Yaguet]

Hi,
I had a similar issue with the fuses, but long story short I found matching value fuses, replaced them and the monitors work, but now I have 2 different issues:

1- The first one may be related as it is a powering issue. Some times the monitors will turn on but won't sound or at a very low level. The issue is "solved" by pushing, twisting and pulling the small volume know in the back. I thought I may have accidentally hit one of the monitors until the issue started happening in the second monitor, which was sitting on its stand for months.

2- I don't know if this is related but now I constantly hear a random clicking, popping, cracking sound with makes it impossible for any serious studio work.

I hope someone has a clue on what to do here...

Thanx

 

[SkywaveTDR]

First I have not worked on these but if you are blowing fuses there has to be a part in the unit that is not up to grade. I would have to guess sit was the filter cap. But it could be other stuff. A Technician should be able to make some tests and tell you where the trouble is. I did not see any advrse advice that Warren was giving and in fact I would agree with him. I am an ex-Teac Technician and a BSEE as well.

 

[SkywaveTDR]

That is strange that a speaker should do that but it all depends on the quality of the design and build. How expensive are these speakers?
If they are cheap you know where they are made so that must be considered. Could be power supply or a bad amp not heat sinked properly. I have seen many flat pack IC's connected to heat sinks with very little heat sink interface paste- that was why I had to change them.

 

[Damian Clark]

Warren Daly, thanks for your experience. I'm also looking to replace the transformer in my VL-A8, and not sure what to look for, but 24.5 x2 like yours. Trying to get one the right dimensions at the correct output seems impossible. Is yours a custom?

 

[SkywaveTDR]

You can buy a toroid transformer easy in most places that is superior to the blown out one in your speaker. I would select a 50% higher current capability. For those that think a larger fuse is the answer- if there is a short in the circuit somewhere it doesn't matter if you put a 20 amp fuse in there it will still blow and also possibly catch fire. If Warren is a BSEE then there is no reason to doubt his solution. These guys are not dummies. I went the course.
Abusive language will just get you kicked out of here. I have seen it happen.
If the transformer is blowing out on more than one unit, then it is time to get to customer service to find out their resolution as this is NOT a fluke occurrence but a flawed design. That means that you should have a new part supplied to you free warranty or not. When I worked at Teac I saw a lot of settlements happen and sometimes they were not to the advantage of the customer. I own a Teac C-1 that was traded for a cheap $70 CD player because the client did not like the sound of the deck. The C-1 was $1500 cassette deck. I did not mind getting it on the employee sale as I was the one who worked on it and it was perfect.

 

[chucklechops]

Please do not insert a higher rated fuse.

Both of mine keep blowing fuses, but now 1 of the units will not power on after the fuse is replaced.
I opened both units, swapping the various boards and transformer around until I found out what the issue was. This torodial transformer has it's primary coils shorted out.

The main amplifier board is supplied by a white connector block, it has 2 black leads, and 2 red leads. The two red leads are 24.5V AC, the 2 black leads are 0V/Ground.
I actually replaced the entire transformer and bypassed the first circuit board (with the relay).

The new fused torodial transformer is giving out 25V AC out. So I connect it the amp board after removed the existing broken transformer. No I will run it to see if this unit will start to blow fuses.

Hi, Warren,

Thought this thread had died. If you're still around I don't suppose you could link me to a suitable replacement part from somewhere like Farnell or Digikey? Pretty sure I can drop in a replacement but I don't really understand transformer specs.
Many thanks in advance.

 

[pots77]

hola mi vl-a5 el potenciómetro de volumen se rompió, (es el azul) el sonido se corta o baja y cuando vuelve no puedo entender el esquema, ¿sabes qué valor tiene? ¡¡Gracias!! saludos desde Argentina

 

[pots77]

hello my vl-a5 the potentiometer of volume was broken, (it is the blue) sound is cut or low and when it comes back I can not get the scheme, do you know what value it is? Thank you!! greetings from Argentina

 

[Martin Nelson]

Hi, does anyone have a part number for the transformer? i'm having the same problem on one of my A5's

Thanks

 

[Larry Youngman]

My monitor Soft start was blowing the fuses had a short. I purchased a generic one from EBAY that was within the AC rating. Modified to fit. All working now.