Soundstream Reference 500sx problem

[azvrt]

I have a 500sx that seems to short circuit when I hook it up to the power supply, as the analogue indicator of the PS instantly maxes out at over 3 ampere, the max indication, so I quickly power it off.

I see this one has been heavily repaired in the past.

Anyway, I once had a Ref 300 and 200s which also short circuited, and on both amps replacing the rectifiers did it for me.

I can't remember what the rectifiers should read on this amp, as it's quite some time ago, but when I did the ohms test I only had 0.00 or 1 (max) on the digital multimeter, nothing else. Usually there are also other values. Many, many legs have 0.00 on them, in several directions. So maybe the rectifiers need to be replaced on this one as well ?

I noticed they are FEP16CT and FEN16CT, I have lots of BT's in stock but they are lower rated. Wonder why Jaime give me so much BT's, while most Ref s / sx amplifiers use the higher rated CT and DT ?
I have some DT's in stock I think, could use those. Or would it be safe to use the lower rated BT's ? Got so many of them...

I see the 160s and 200s use BT, but most (if not all) other models use CT or DT, and more often DT than CT. Wonder what I will ever use the BT's for ??

[1moreamp]

You can send all of your BT's to me if you like lol lol..


Most amps like SoundStream only have 20 to 35 volt rails so lower PIV rated diodes should just fine my friend

Using a 600 PIV rated diode means the engineer spec'ed the highest rated device possible in hopes of getting the best possible PN junctions off the silicon wafer, and inside the amp.

[azvrt]

Same as the IRFD9110 on the Adcom
I'll ask Jaime what he thinks but it sounds very reasonable, thanks.

But do you think there's something wrong with the rectifiers, since they only read max ohms or 0.00 ohms, and on a lot of legs 0.00 ?

[Perry Babin]

In the circuit, you will read 0.000v on diode check across the outer legs because the transformer windings are connected to those legs. Although there are a few exceptions to this, most amps that use positive and negative center-tapped rectifiers connect the transformer windings to the outer two legs.

[azvrt]

Great information Perry.
I'll have to check but I think I have lots of positions on which it read 0.00 ohms.
When you're saying that I can expect to find these 0.00 readings across the outer legs, do you mean in both directions (positive - negative and negative - positive) ?
Would that imply that each rectifier would show 0.0 twice, when measuring across all legs and in both directions ? I think (but I could be wrong) I had more than twice 0.00 for each rectifier.

[Perry Babin]

They will read 0.000v in both directions on diode-check.

If you read 0.000v on diode-check from the center-outside legs as well, the rectifier (or one in parallel with it) is likely shorted. The only other thing likely to make it appear that there is a shorted rectifier is shorted rail caps.

[azvrt]

I think, but I'd have to check, that I had 0.00 in at least 4 positions / directions on each rectifier.
I will simply replace the rectifiers and see what happens then.

[Perry Babin]

When you remove it, re-check it.

[azvrt]

By that, you mean check them again with the ohms test, and if all four of them turn out to be good, I have to look for the problem elsewhere, right ?

If one of them is bad, I'll like have found the problem ?

[Perry Babin]

Yes to both.