stage accompany ppa-1200 amp

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cunningham

Member
Joined 2004
If setting the bias is all, you don't need a scematic. Just turn the bias pot so that the outputs are in cuttoff, then measure the voltage across the emitter resistor, 0.1-0.5Ohms. tweak the pot until you see voltage begen to develope accross the resistor. This is where you want to bias. Disconnect one of the output collectors, and insert an ammeter to be sure.
 
nigelwright7557

nigelwright7557

Member
Joined 2008
murtonpikesystems.co.uk
lumanauw said:
Anyone got a schematic for Stage Accompany power amp? This is an older unit, blue casing, 2 toroid power transformer, has 16 pair of 2SC5200 per channel. Blown up, some resistors are burnt.
Click to expand...


I suspect the bias is set using set resistor values after they had a pot in the prototype.

I wouldnt bother for 3 degrees either unless the 3 degrees is 3 degrees above 120 degrees C !

It will be quite a bit of hassle to set the bias plus you might make a mistake and blow the output transistors.

Is it really worth the hassle ?

The last time I set up a bias I blew 6 MOSFETS and it cost me around £15 to replace them.......
 
W

Webbie

Member
Joined 2007
sa-vintage.com
Hello,

Quoted from my site, mite be a help for you all if want to buy this beautifull apparatus:

The PPA 1200 is the best amplifier SA has ever built.
One of the nicest things of the PPA is the build in crossovers.
The presets in the PPA 1200 have been coupled to electronic internal crossovers.
It’s even possible to develop your own crossover with the existing soft and hardware.

Unfortunately at present time an amplifier with a capacity of 600W RMS in 4 ohm and a weight of 36kg is no longer suitable for PA use.
The use of large number of electronic components, from which the amplifier is build, is also no longer profitable.


Buying second hand:

If you want to buy a second hand PPA 1200, it’s best to look at a PPA with a serial number higher than 271 (last four digits of the serial number).
It has interchangeable crossovers. On the outside the unit is recognizable from the “Input Link” at the back of the amplifier.

PPAs with a serial number less then 272 do not have an “Input Link” and also doesn’t have interchangeable crossovers.

The PPAs (with serial number higher then 271) have got many advantages in contrast to the first series with the lower serial numbers:

- thicker power cord
- interchangeable crossovers
- 12V relays, instead of 6V relays
- improved 5V power supply
- no annoying audible 50Hz hum anymore
- much better reliability of service
- better serviceable


Greetz Webbie...
 
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