I bought a used Parasound HCA 1000A from a pawn shop. They said it worked--it doesn't. However, I only paid $100 for it and it is worth fixing.

The problem may not be significant--when I opened the case, I found 5 fuses, most of which were blown. Off to Radio Shack for replacements. Problem: the numbers on the blown fuses don't perfectly match the numbers on the RS fuses. The clerk was nice, but barely more knowledgeable than I. I don't want to make things worse, so (and I absolve each of you of any liability), what are the chances the following fuses are approriate?

Amp T5l 250V (4 of these, grouped in the same basic location)
RS 5 amp 120 volt (this "match" seems the most suspicious--"120 volt"?)

Amp 1A 250V (1 of these, behind and apart from the above)
RS 1 amp 250 volts

Amp T6,3AL 250V (1, on the outside case where the power cord goes)
RS 3 amp 250 volt

Obviously, I know nothing about this and need help. Fuses may not fix the problem (what caused the fuses to blow in the first place?), but it is a starting point.

Thanks in advance for your guidance.

In case you don't have an answer before Monday night. I will get on a data base called FEDLOG on Monday at work and I should be able to cross reference your originals and come up with the fuse ratings that you need.
Richard

What made the fuses blow is too much current flowing through them for a long enough period of time to melt a portion of the fuse element (or vaporize part of it).

In addition to that true but useless reply, I also offer:

Beings I don't have a schematic of your amp, I will make some generalizations.

The power line fuse, is in series with the power cord, power switch and the primary of the transformer(s)

There are usually fuses for the main positive and negative DC voltage supplies to the output stage (and maybe other stages) of the amp. Often, there is a pair of fuses per channel.

Sometimes there is a fuse in series with the output of the amp. This is not always present.

If you are playing the sustem realy loud and into a low impedance for a long time, the output fuse may blow. Sometimes, a DC voltage fuse may blow instead especially is the wrong value, and/or type, of fuses are installed.

If an amp component fails, this may cause fuses to blow. A shorted output transistor will tend to take out a DC voltage fuse. A bad main supply filtering capacitor could cause the AC line fuse to blow, as would a short in a transformer.

Old fuses will tend to fail at lower current values that what they are rated for, expecially if they have had numerous current "surges" that came close to, but not quite, blowing the fuse.

If a previous (ab)user of the amp had replaced blown fuses with any old value that was on hand that did not immediatly blow, then many of the fuses and/or amplifier circuit components may be abnormally stressed and weakened.

As to what could make several fuses blow, I'm guessing here even more. A AC line power surge (including lightening strike nearby) might do it, as would an EMP from a "nearby" nuclear explosion.

In regards to fuses themselves, in addition to the rated current and voltage ragings, there is another fuse rating: fast blow, slow blow and medium blow. This refers to how fast the fuse will react to an overload of current.

AC line fuses often are "slow-blow" to allow for a brief current surge when the amp is turned on (transformer inrush current and current surge due to the initial charging of the DC voltage supply filtering capacitors).

Let us know what happens when you replace the blown fuses and turn on the amp.

Paul

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the 1derful1

[This message has been edited by Paul J. Stiles (edited April 18, 2003).]

Paul & Richard,

Thanks for the ideas. I don't expect to have this solved by Monday, so, Richard, if you have some way of checking, I would be indebted. Paul, I am anxious to try the fuses I have, but, as I said, I don't want to do more damage.

Could there be a Parasound 1000 wiring diagram out there someplace that would answer the question? As Paul suggested, what if I am matching wrong fuses? Gonk suggested trying to get a fuse package from PS, and I have called a dealer, but no response. Gonk also asked whether the 10 year warranty was transferable--anyone have experience with that?

Anyway, you guys are the greatest. I will keep checking the board. Thanks.

Why not contact Parasound?

Contacting Parasound: Way too simple to be considered! ;0)

After my last post, I found the PS warranty information--no transferable warranty.

I also found a tech contact number and called. Guess I hadn't tried that earlier because I figured they would not be polite to someone who bought used gear and had bonehead questions. Boy, was I wrong. Terrific help, and incredible support. Learned the "T" in the first fuse is "medium blow" (as opposed to fast or slow). He said the 120V vs. 250V was no big deal. Bad news: In his opinion, the problem is probably more than the fuses, and that an "output transister" probably blew and that could have started a "cascade" of other problems. His repair cost was less than $200, so, given what I paid, I could spend that and not wind up upside down on the amp.

Will find a 5 amp slow or medium blow fuse tomorrow and see what happens.

[This message has been edited by michaelstano (edited April 18, 2003).]

Make that "not wind up upside down."

More incredible news: This afternoon, I wrote to PS regarding the warranty, and just after I clicked the send button, I found the on-line warranty that said "not transferable." Figured whoever read my message would say, "the dummy can't read," and that would be that. Wrong. After my last post, opened my e-mail to find a reply from PS indicating that they wanted more info but that they might help with repair. Is PS long on customer service or what? (Reminds me of stories I've heard about Outlaw.) So, I will not be messing with fuses until PS definitely says they can't help me.

Those fuses will work fine. The current rating is what matters on the fuses.

Michaelstano,

What is the status of you amp? Inquiring minds want to know.

Paul


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the 1derful1