Exposure iv pnp npn ?

[Gervais Cote]

A thing is sure : the electrolytic capacitors really improved a lot over time in terms of performance so looks logical that Exposure recommend them now, especially if only low performance ones were available back in the 80’s.

 

[colasblue]

Actually the ones they used, both in the 80's and now are about the cheapest phillips/bc components/vishay series you can get. The name changes over time but the cap is the same.

If a tant was original equipment pretty much an electrolytic could improve on it in some sense since tants have huge ESR.

 

[john & Jake]

Hi, Just powered up the exposure after testing with a bulb and taking DC and bias readings. 3mv dc and 9.5mv dc right and left.
Bias around 3mv both channels. All within spec apparently.
One board is still awaiting two resistors but I've made up a temporary pair.
Playing music now through a cheap pair of gales bought for testing purposes.

If I can fit some speaker protection, I'll plug in the Majik 140s.

Many thanks to all who advised me here as it was invaluable.
And must mention and thank Tony from Exposure who went above and beyond to encourage me to have a go and for his expert knowledge. Thanks Tony.

 

[a.palfreyman]

What was the problem?

 

[john & Jake]

Several burnt resistors and one exploded transistor were the only visible signs, very large amounts of dc on the outputs.
So I changed all the transistors and tant caps, replaced faulty and incorrect resistors.

 

[Gervais Cote]

Hi, Just powered up the exposure after testing with a bulb and taking DC and bias readings. 3mv dc and 9.5mv dc right and left.
Bias around 3mv both channels. All within spec apparently.
One board is still awaiting two resistors but I've made up a temporary pair.
Playing music now through a cheap pair of gales bought for testing purposes.

If I can fit some speaker protection, I'll plug in the Majik 140s.

Many thanks to all who advised me here as it was invaluable.
And must mention and thank Tony from Exposure who went above and beyond to encourage me to have a go and for his expert knowledge. Thanks Tony.

Looks like a lovely amp to me...........
Here is the slow start/speakers protection fitted in my IV dual mono :

 

[Gervais Cote]

And here is the final result, if that may help :

partager une image

It’s been done by one of my friends so can’t give you detailed instructions though.

 

[john & Jake]

Hi Gervais, looks like a nice module, do you know a supplier.

 

[Tonewheelkev]

Looks like a lovely amp to me...........
Here is the slow start/speakers protection fitted in my IV dual mono :

Would like to know more about this board.
I have 6 unprotected channels into Linn Isobariks.....and have been lucky so far.
This needs some thought I suppose.

 

[Gervais Cote]

Hi Gervais, looks like a nice module, do you know a supplier.

Here you go :

https://hifimediy.com/product/speaker-protection-circuit-connexelectronic/

 

[john & Jake]

I think they only have one on that link. I found this, the Chinese makers.
https://connexelectronic.com/product/spc1/

They will do a single pole version for larger amplifiers on request.

 

[Tonewheelkev]

Several burnt resistors and one exploded transistor were the only visible signs, very large amounts of dc on the outputs.
So I changed all the transistors and tant caps, replaced faulty and incorrect resistors.

Can I ask which was the exploded transistor please?
My Dual IV....doing the Mids in an active system.....misbehaved yesterday, and 'took out' one of the mid drivers on my Isobariks.
Any tips appreciated on what to 'look' for here??