All of your listed transistors (if I decoded your part numbering correctly) are available for Mouser UK, and I would suspect any of the main components suppliers (Mouser, Digikey, Farnell, RS Components, etc.). Part numbers I looked up were MPS6561, MPSA42 and PN4250. All in stock.
I would buy from reputable suppliers and avoid places such as Dalbani, etc. You don't need to have counterfeit components adding to your troubles.
If that amp is like the newer thresholds, you simply remove the screws holding the heat sinks to the bottom of the chassis, remove the screws holding it to the faceplate and then the heatsink assembly pops right off. So you can work on the channel with it flat on your bench. The red lines in the picture below indicate where the screws would go into the heatsinks. It looks like the RCA is mounted to the back panel.
You can use longer leads to power it up this way as well. I suspect you have V+, V- and GND going to the channel. The more astute Threshold enthusiast may notice something out of the ordinary about the channel in the picture below 🙂
Gary's suggestion of silicone wire is good. This stuff is pretty nice and innexpensive:
https://www.amazon.com/gp/product/B01M7NWX7A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
For the signal stuff, if it is in good shape just leave it. It is probably a shielded coax.
The parts in the circle are what you should expect to see on the front stage board.
Again, identifying the parts that are blown and their purpose should lead you in the direction of finding out where the issue lies.
You can use longer leads to power it up this way as well. I suspect you have V+, V- and GND going to the channel. The more astute Threshold enthusiast may notice something out of the ordinary about the channel in the picture below 🙂
Gary's suggestion of silicone wire is good. This stuff is pretty nice and innexpensive:
https://www.amazon.com/gp/product/B01M7NWX7A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
For the signal stuff, if it is in good shape just leave it. It is probably a shielded coax.
Not a terrible idea. Testing the potentially good channel and then fixing the bad channel would be the way to start.
The parts in the circle are what you should expect to see on the front stage board.
Again, identifying the parts that are blown and their purpose should lead you in the direction of finding out where the issue lies.
I agree Mike with all you have said, I see you show the channel with the new FE pcb as well. As well as having the OS board nicely cleaned up. Also looks like you might have fitted new OS emitter resistors.
Thanks for the Advice Dennis .
The revised pcb’s are definitely the better option but it’s beyond my skill set to know how to populate the boards etc .
Andy
You guys are just amazing.
I have now been off the new revised boards and more .
Yes, that mess needs to be tidied up a bit, as you disconnect things, as I said document every connection point A to point B and double check with the schematics.
The rebuild will be a great learning curve - remember slow and steady wins the race.
The rebuild will be a great learning curve - remember slow and steady wins the race.
Sorry Pars I wrote one of the part numbers wrong ( mps6561 ) should be mps6571 , which I can’t locate, I’m also confused by the mpsA42ebc and 018mpsA42 , are they the same thing ?
The transistors in the original Stasis 2 FE are:
MPSA42
MPSA92
PN4250A
MPS6571
MPSA42
MPSA92
PN4250A
MPS6571
The schematic shows the transistor types, whoever has worked on your amp has done some substitution it seems.
So you have:
MPSA42 - disregard the 018
MPS6571
BC550C
PN4250
Looks like the BC550C is there instead of the MPSA92
So you have:
MPSA42 - disregard the 018
MPS6571
BC550C
PN4250
Looks like the BC550C is there instead of the MPSA92
Yes mate that is correct.
I can’t find the 6571 anywhere other than eBay or one other place called Electronic surplus in USA , as I only need 2 I might just remove them from the board and test them with my Peak tester ( should do the job? )
It would be nice to get these original boards working now that I’ve started .
I can’t find the 6571 anywhere other than eBay or one other place called Electronic surplus in USA , as I only need 2 I might just remove them from the board and test them with my Peak tester ( should do the job? )
It would be nice to get these original boards working now that I’ve started .
No, that is not correct as the MPSA92 is a PNP and the BC550C is an NPN.
the 6571 is obsolete, but there will be an equivalent.
Yes use the Peak to check the transistors by all means.
the 6571 is obsolete, but there will be an equivalent.
Yes use the Peak to check the transistors by all means.
Just check the position of the MPSA92, there is only one in the circuit.
The amp wont work with an NPN transistor in that position - the other working channel must have the correct transistor in that place - so carefully compare between the two. What makes it hard is the fact that there is no component silk screen on the pcbs to identify the components.
This is where you will need the schematic printed out and carefully trace the connections to see what transistor is what according to the schematic.
The amp wont work with an NPN transistor in that position - the other working channel must have the correct transistor in that place - so carefully compare between the two. What makes it hard is the fact that there is no component silk screen on the pcbs to identify the components.
This is where you will need the schematic printed out and carefully trace the connections to see what transistor is what according to the schematic.
There is 1 mpsa92 on each board . There are 2x c550c’s on each board and they are right next to the damaged resistors
It sure does, orientate the flat on the transistor body to be facing the same way as the one you are replacing for the same type of transistor. google the transistor datasheet that will give the pin out data. The Atlas tester will also tell you the transistor type (NPN or PNP) and what pin each of the three coloured leads are connected to for C B E.
Note, some equivalent transistors could have different pin outs if using any.
Note, some equivalent transistors could have different pin outs if using any.