Inkel pa-848 100v amp

[Canalboat Tom]

Hi has anyone got any experience with the above amplifier? It has 2 fuses on the front, 25a and a 5a, keep having issues with the 25a fuse keep blowing. But not sure what that fuse is actually protecting and so where to look for the fault. The amp.can run of 240v or 24v, currently using the amp on 240. 

 

Cheers for any help.

[themadhippy]

Quote

But not sure what that fuse is actually protecting and so where to look for the fault

just a wild guess from looking at the front panel id say its for the 24v DC input

[Canalboat Tom]

1 hour ago, themadhippy said:

just a wild guess from looking at the front panel id say its for the 24v DC input

Thats what I had guessed. However they are using it on 240. The only thing I could think is if there's a transformer to take the 240 down to 24v dc. 

[sandall]

2 hours ago, themadhippy said:

 looking at the front panel id say its for the 24v DC input

Indeed it's labelled "DC 24V", which doesn't explain why it's blowing when on mains power. No experience of this amp (& can't find anything useful online), but the DC fuse should just sit between the DC input socket & the output of the power-supply, so with no 24V connected there shouldn't be any current flowing (even if something has gone short-circuit). Does the amp work if you just remove the fuse?

[David Duffy]

The DC fuse is likely used for mains and 24V operation. If it's anything like the TOA amps, the 24V DC input feeds into the rectified transformer supply via a separate diode. Here's how the TOA A500 series do it.

[Canalboat Tom]

1 hour ago, sandall said:

Indeed it's labelled "DC 24V", which doesn't explain why it's blowing when on mains power. No experience of this amp (& can't find anything useful online), but the DC fuse should just sit between the DC input socket & the output of the power-supply, so with no 24V connected there shouldn't be any current flowing (even if something has gone short-circuit). Does the amp work if you just remove the fuse?

Without the fuse the amps not working. 

30 minutes ago, David Duffy said:

The DC fuse is likely used for mains and 24V operation. If it's anything like the TOA amps, the 24V DC input feeds into the rectified transformer supply via a separate diode. Here's how the TOA A500 series do it.

Thats what I was thinking. Just trying to work out whats causing the fuse to go. The last time it went apparently there was a hot signal coming into the amp.

[sunray]

I have had a couple where one output transistor has gone s/cct C to B (effectively a diode between C&E) which seems to 'work ok until the volume is cranked up', or so the docket says.

[sandall]

10 hours ago, David Duffy said:

The DC fuse is likely used for mains and 24V operation. If it's anything like the TOA amps, the 24V DC input feeds into the rectified transformer supply via a separate diode. Here's how the TOA A500 series do it.

Interesting, I checked my A300(?) series TOA ((mains + 12V DC) & the fuse is in series with the DC socket, but it sounds that the Inkel is like your TOA circuit, so it's probably 1 or more o/p transistors gone short-circuit.