Acdom 545 -- Left Channel Not Working ....?

[Stoopalini]

I bought an Adcom GFA-545 about a month or so ago and have been using it to power my 100 Watt DVC 12" Realistic Ported Sub. I bought the amp for a Sonosub project that has been put on hold until my 12" Shiva shows up.

Yesterday, 2 Aura Bass Shakers showed up and I finally got to check them out today. I disconnected my passive sub and hooked up the bass shakers. Time to test 'em out!

When I ran an LFE sweep, only one shaker shook (say that 5 times fast ).
So I swapped the shakers, and the problem moved to the other one.
Then I switched the inputs and the problem stayed on the left side.

This is a pretty good indication that my problem lies in the Left channel of the Adcom.

My question is about the fuses on the back of the unit. I bought this amp used, and when it arrived one there was an empty fuse hole on the back. When I tested it, it worked fine; so I figured this must be a hole to keep a spare fuse in and left it empty.

The back is setup as follows:

Fuses 1 & 2 are on the bottom left. Both are inserted and fine.
Fuse 3 is the AC fuse. It is on the right, above the power wire and it's fine.
Fuses 4 & 5 are beside each other on the bottom right. #4 (right) is present and fine. #5 (left) is missing.

Just to test it out, I moved #4 into #5's spot, and the amp did not act any different :?

So if anyone has one of these, or experience with one, could help me out, I would sure appreciate it. I looked on http://www.Adcom.com, but this unit is no longer listed .

I'm about to remove the cover and see what I can find out, so wish me luck......

Thomas.

[Lexman]

Thomas, I can only recommend finding someone very familiar with the Adcoms to comment on this. Be careful going inside, I don't know about the shielding on the power supply and such! If your unaware, power supplies can retain power even in an off and unplugged state-

Lex





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[Stoopalini]

Hey Lex,

Thanks for the warning, but I never did get inside it. The cover is held on by what I believe to be torx screws, and I don't have any torx bits. So I'll have to wait until tomorrow to check it out.

About the cap's holding power: yea, I 'll watch out for those. My Brother and Uncle both worked in the electronics field for years and hopefully we can figure out what went bad.
I already called my Bro and he said the "Mosfet Supply" (whatever that is) is common to go out and we should check that 1st.

So I've put it off until tomorrow.

In the meantime, I got the Aura Bass Shakers installed into my couch. I hooked them up in series to the Adcom's channel that is working.
Kind of an interesting touch to the system -- the physical aspect that is. Without a sub running though, it's kind of strange -- just feeling the low without actually hearing it.

Oh well, hopefully soon my Shiva will arrive and I'll be able to complete my low end.

Thomas.

[Lexman]

Sounds like a great plan Thomas. You will enjoy your Shiva when it comes

Lex





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[Andrew Pratt]

well at least you've got some great help on the way. If you like that tactile feel you're going to love the feeling of a shiva when its rocking

[Digital Bob]

Thomas,

I'm going from (a distant) memory here so PLEASE keep that in mind as you read the following:

If I recall correctly the 545, like most the Adcoms, have a *#@#load of screws on the top to remove the cover. They made it even tougher by making them "Allen" heads. What a pain :M You should be able to use a hexkey/allen wrench of the right size to remove them.

About the fuses..hmmm. It used to be that those amps would pop them on a semi-regular basis. For years I would have to remove the top and replace one or more of them. BTW- I remeber them having TWO fuses per channel (positive & negative rail?). Usually they would pop only one of the two.

NOTE: The amp would often still play softly with only one of the fuses working (or installed!) because of the A/B nature of the design, I believe. In other words the "opposite half" of the output stage remains on at low levels to facilitate the Class A part of A/B. So even with one fuse missing you could get some tiny output on occason. However, once you placed a real demand on the amp this immediately disappeared. This may explain your "testing" the amp with the fuse missing and passing it, then when you hooked up the Auras...

One weird thing though, I distinctly remember the fuses being on the INSIDE of the unit, not the back panel. Maybe they had so many popped fuses that in later models they moved the fuse holders to an external position for convenience. Don't know.

Hope some of this helps,




dB

[ThomasW]

I have a pair of 545II's, used for the "effects" channels. These have only one external fuse, it's of course for the main in. Any extra fuses are just included with the owners manual, not "stored" in the chassis. The chassis screws are Allen head, not Torx. And unfortunately it sounds like time for a trip to the "hospital"




theAudioWorx
Klone-Audio

[Digital Bob]

UhOh! I got my Thomas's confused there for a minute :E I'm editing parts of this message to make more sense (hopefully). Now that my brain is functioning I realize that Stoopalini and ThomasW are not the same person. Duh, Bob!



Thomas (can I call you Stoop?),

Sorry for the confusing posts, let me try it one last time. Give this a shot...

1) Remove the two fuses (you called #1 & #2) and place them in the corresponding spots on the other side of the amp (you called #4 & #5).
[Note: Move BOTH fuses from one side and fill BOTH fuse slots with them on the other side]

2) Move your speaker wires over to the other channel as well (the one you now have 2 fuses in).

3) Play some music and see what happens


My guess is that the amp will now work on that channel.

These amps require two fuses per channel and your test to swap of #4 to #5 , although reasonable, still left only ONE of the fuse slots filled for that channel. If the fuse holders are on the back panel, then this should literally be a 60 second experiment.
Let us know what happens.


Thomas W,

My use of the term "fuse holder" may be misleading (and incorrect? h: ), I use it to mean an active, working, wired, socket for a fuse to do it's job in. Not a place to "hold" extras.


Hope this helps,




dB

[Stoopalini]

Well,

Bob was right on the fuse thing. I took Fuse #1 out and put it into #5's spot. The left channel started working and the right stopped :B
The right channel still had some noise like he said it would, but not enough to push a transducer.
I guess I didn't notice this before due to the fact I was pushing a Dual Voice Coil woofer with it.

So I went to Radio Shack and bought a fuse case/holder, but it's too long to fit into the Adcom chassis; the back of it hits the heat sink when its seated fully. So I got the # for Adcom parts and am going to order a few extra fuse casings.

Thanks for everyone's input, I'm Soooooo glad I do not have to replace this amp

Thomas.

[Digital Bob]

Thomas,

Glad to hear it worked out well. It's a great sounding amp for the money, enjoy.




dB