Attn Ron, Gareth etc. HK Projector PA system - fan question ...

[Arfa Daily]

Anyone know the correct voltage for the fan fitted to these? Just had one in
with a new (??) fan hanging loose in it. Job ticket claims that the owners
replaced the fan, and then it smoked ... I'm not sure what they had done,
but they had twatted a set of o/p tr's on each board, and the smoke had come
from one of the 0R22 emitter resistors, due to the 15A fuses that had been
fitted ... :-(

Anyways, amps all repaired now, but their new fan, which is 24v, seems
reluctant to start. Measuring quickly across it, shows just about exactly
12v. Haven't got full schematics that show the fan connection, so without
pulling the board that the fan is connected to all back out to follow print
around, I don't know if it is a 'controlled' fan, and there is something
wrong with the controlling circuit, or whether it's right, and the fan
doesn't actually start until the thing hots up a bit, or whether it should
be a fixed 12v fan, and they've just got the wrong one.

Funny isn't it. I repair loads of HK PA amps - Actors and Lucas's and these,
and I've never noticed what voltage the fan is. But I'm pretty sure from
memory, that they usually run at full chat all the time, as I'm also pretty
sure that they normally start up at quite a low input voltage, when you are
bringing a repaired one up on the variac.

So, anyone know for sure ?

Cheers

Arfa

 

[PeterD]

Anyone know the correct voltage for the fan fitted to these? Just had one in
with a new (??) fan hanging loose in it. Job ticket claims that the owners
replaced the fan, and then it smoked ... I'm not sure what they had done,
but they had twatted a set of o/p tr's on each board, and the smoke had come
from one of the 0R22 emitter resistors, due to the 15A fuses that had been
fitted ... :-(

Anyways, amps all repaired now, but their new fan, which is 24v, seems
reluctant to start. Measuring quickly across it, shows just about exactly
12v. Haven't got full schematics that show the fan connection, so without
pulling the board that the fan is connected to all back out to follow print
around, I don't know if it is a 'controlled' fan, and there is something
wrong with the controlling circuit, or whether it's right, and the fan
doesn't actually start until the thing hots up a bit, or whether it should
be a fixed 12v fan, and they've just got the wrong one.

Funny isn't it. I repair loads of HK PA amps - Actors and Lucas's and these,
and I've never noticed what voltage the fan is. But I'm pretty sure from
memory, that they usually run at full chat all the time, as I'm also pretty
sure that they normally start up at quite a low input voltage, when you are
bringing a repaired one up on the variac.

So, anyone know for sure ?

Cheers

Arfa

There are fans designed to work with 12 to 24 volts (they regulate
internally) which might fit your needs.

I'd guess with 12v there, it needed a 12v fan...

 

[Arfa Daily]

Which diags do you have? Mine are dated 30.5.2000. there's a fan plug
connected to pin 6 on connector FCC16 via aa IN4007 and a 150R 5watt
resistor (R85). Pin6 would appear to go to an AC side of the bridge reccie
via a 10R 1 watt (R3)

Any help? I can send you these dags if they will be of use.

Ron

That sort of looks like what I can see, so yes please, go for it with the
diags to the usual email addy, Ron. Thanks

Arfa

 

[Arfa Daily]

That sort of looks like what I can see, so yes please, go for it with the
diags to the usual email addy, Ron. Thanks

Arfa

OK. Well, it seems to be just a fixed voltage supply, derived via the 10R,
the 150R, and a single 1N4007, with a 470uF filter cap on the end. Both the
R's are ok, and the filter cap is ok, and there is almost exactly 12v at the
fan connector. Also, the filter cap is only rated at 25v, so, as far as I
can see, that all points to 12v being the correct supply for a fan that runs
all the time, making it a 12v fan. Therefore, the 24v fan that the owner
obtained as a replacement, would seem to be wrong. I wonder what he felt was
wrong with the original fan ? I repair lots of these HKs, and I don't think
I can ever remember having a faulty fan in one.

Arfa