This is an old version black amp from the 80s.
I found this thread: PPI 2125 missing parts with related amplifier.
This amp I'm looking at is using S2N6487s in the PS, but I believe it should have been S2N6488s as they were previously replaced. Either way theres one BJT missing, and a few other parts as well look a bit different and wore out compared to the above thread.
Anyone have a schematic by chance?
Another question. As I comb through my PPI amps, I find that some are using 2n6487/2n6490, and others are using 2n6488/2n6491. I already ordered 100+ of the 88/91s from Avnet.
Can I use the 88 in place of the 87s, and the 91s in place of the 90s? To me the voltage ratings are just higher on the 88/91s.
Easy data sheet showing them all: https://www.alliedelec.com/m/d/34bc368bea952b9eaf1799a01f3d3329.pdf
I found this thread: PPI 2125 missing parts with related amplifier.
This amp I'm looking at is using S2N6487s in the PS, but I believe it should have been S2N6488s as they were previously replaced. Either way theres one BJT missing, and a few other parts as well look a bit different and wore out compared to the above thread.
Anyone have a schematic by chance?
Another question. As I comb through my PPI amps, I find that some are using 2n6487/2n6490, and others are using 2n6488/2n6491. I already ordered 100+ of the 88/91s from Avnet.
Can I use the 88 in place of the 87s, and the 91s in place of the 90s? To me the voltage ratings are just higher on the 88/91s.
Easy data sheet showing them all: https://www.alliedelec.com/m/d/34bc368bea952b9eaf1799a01f3d3329.pdf
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Btw this amp does power on but the ps bjts get hot pretty quick. Draws 4.5 amps at idle. Even though its missing a bunch of large caps.
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Just my Gophert 20A supply. I set it to about 5A and it does OCP. I haven't burnt up a part/amp on the bench with this supply at all yet. For a Chinese digital supply I actually like it a lot.
This looks similar to the first generation orion. Those amps would not power up normally if there was any current limiting. Try it on a power supply that will not limit current.
Yes it reminds me of the last old Orion I worked with. This amp powers up just about fine actually. Almost immediately. The issues are; mismatched PS components, missing caps, disconnected bridge diodes, and the PS BJTs get warm/hot pretty quick as its idling at 4.5A.
Do you think its normal for these older style PPI/Orion amps to pull that much idle current?
Someone left this amp pretty badly but I actually think it works in it's current condition.
Do you think its normal for these older style PPI/Orion amps to pull that much idle current?
Someone left this amp pretty badly but I actually think it works in it's current condition.
The missing caps could be a problem.
Any heating of the output transistors?
Did you try it without any limiting and it still draws the same 4.5A?
Any heating of the output transistors?
Did you try it without any limiting and it still draws the same 4.5A?
Theres no limiting going on. I set my PS to 5A and the amp starts up then idles at 4.5A. Its actually not engaging OCP. Idling at 4.5A under 14.4vDC.
I'm going to make some brackets to clamp any PPI amp FETs/BJTs to their syncs while the cover is removed. Picking up some stock from Homedepot later today.
The output/channel side seems to be 'clean'. Nothing seems shorten, not getting hot, never serviced in that area.
I'm going to make some brackets to clamp any PPI amp FETs/BJTs to their syncs while the cover is removed. Picking up some stock from Homedepot later today.
The output/channel side seems to be 'clean'. Nothing seems shorten, not getting hot, never serviced in that area.
Question #3:
Any idea what the value is of the large horizontal cap between some of the PS BJTs? Mine is missing.
Link to image: https://www.diyaudio.com/forums/att...-ppi-2125-missing-1447436606062-880366495-jpg
Any idea what the value is of the large horizontal cap between some of the PS BJTs? Mine is missing.
Link to image: https://www.diyaudio.com/forums/att...-ppi-2125-missing-1447436606062-880366495-jpg
