I have a couple of Parasound HCA-1500As here and both have blown outputs. The previous owner ran them bridged to a pair of 4 ohm speakers which had too low of an impedance.
Anyways I’m rebuilding both, replacing all outputs and the drivers are measuring funny so I want to replace them as well. I already picked up all of the outputs. According to the schematic the outputs were supposed to be 2sc4029 being driven by the 2sk1058 and then the compliment was the 2sa1553 being driven by the 2sj162.
Well those part numbers are not in either of these amplifiers. These have mjl21194 being driven by 2sk1529 and the mjl21193 being driven by 2sj200. So picked up 16 of each mjl21194 and mjl21193. Now I need to find replacement for the 2sk1529 and 2sj200. I thoroughly do not trust anything on eBay unless someone knows of a seller that has truly authentic devices. Everywhere is out of stock and they were getting quite expensive, b+d had them at $18 each!
I’m attaching a photo to show the circuit. Any help with finding good replacements would be greatly appreciated! I happen to have one pair of each in my stock so I can do one, but need to do the other.
Thank you,
Dan
Anyways I’m rebuilding both, replacing all outputs and the drivers are measuring funny so I want to replace them as well. I already picked up all of the outputs. According to the schematic the outputs were supposed to be 2sc4029 being driven by the 2sk1058 and then the compliment was the 2sa1553 being driven by the 2sj162.
Well those part numbers are not in either of these amplifiers. These have mjl21194 being driven by 2sk1529 and the mjl21193 being driven by 2sj200. So picked up 16 of each mjl21194 and mjl21193. Now I need to find replacement for the 2sk1529 and 2sj200. I thoroughly do not trust anything on eBay unless someone knows of a seller that has truly authentic devices. Everywhere is out of stock and they were getting quite expensive, b+d had them at $18 each!
I’m attaching a photo to show the circuit. Any help with finding good replacements would be greatly appreciated! I happen to have one pair of each in my stock so I can do one, but need to do the other.
Thank you,
Dan
Attachments
This is strange because 2sk1058/2sj162 have different pin out than 2sk1529/2sj200. Therefore, it is either one or the other but not interchangeable. Also, 1058/162 are lateral mosfet but not 1529/200...
I bought my 2sk1530/2sj201 (higher power version) From Ampslab web site. However, I have myself enough parts to help you.
Alfet mosfet are now obsolete but Exicon sells the equivalent.
Fab
I bought my 2sk1530/2sj201 (higher power version) From Ampslab web site. However, I have myself enough parts to help you.
Alfet mosfet are now obsolete but Exicon sells the equivalent.
Fab
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Thank you for the suggestion, but doesn’t look like they’re available anywhere.
Oh wow that is strange, I never even thought of looking at the pinout as I assumed it was the same. The amplifiers have been running this way for years and years and as far as I know these devices are all original. I’ll look for the Exicon parts. Are you suggesting you may have the 2sk1530/2sj201 to sell me?
Dan
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Exicon have same pin out as the 2sk1058/2sj162 thus different from 2sk1529/2sj200.
Yes I could sell you 2sk1520/2sj201 but from your picture I am afraid they might not fit because they have larger package than 1529/200 ....
Fab
Yes I could sell you 2sk1520/2sj201 but from your picture I am afraid they might not fit because they have larger package than 1529/200 ....
Fab
Hmmm thank you, it’s definitely an option. They would fit in the space, but I would need to drill and tap new holes in the heat sink for them to mount.
Any other options? Anyone.
Dan
Any other options? Anyone.
Dan
If this is an option and you do not have other ones then I can give you 2 pairs and you only pay for shipping. I do not plan to use mine anyway.
Fab
Fab
I think the Lateral drivers will work as bias adjust for the bjt outputs because of negative tempco.
If You fit verticals with positive tempco it may result in thermal runaway.
BR
Figge
If You fit verticals with positive tempco it may result in thermal runaway.
BR
Figge
I’m sorry, that went over my head a bit could you please explain the negative/positive tempco? What vertices would have positive tempco?
Dan
You and the previous fixer, are winging a re-design by the looks of it,
I would agree & recommend to use a lateral such as the ALF08P16V and ALF08N16V and not the 2sk1529/2sj200 vertical types, or you will have to re-design the thermal compensation part of the design.
But they do not exit so try ECX10N(p)20 in a TO-247, check the package against the original TO-3P type for fit.
TO-247 is 16.26 max wide and pitch of 5.25
TO-3P is 15.9 max wide and pitch is 5.45
same pin g,s,d
The best choice for o/p would be 230W MJL4281A/4302A, try the slower MJL21193,4 since you have them.
Always check the data sheets and verify pin-outs.
Good luck
Well I'll try to explain this tempco-thing.
There are propably a lot of experienced people here that do this a lot better than me...
When Vertical fets as well as BJT's gets warmer Vgs and Vbe changes and more current will flow.
Bias network usually compensates for it.
Lateral fets works the opposite way, and sort of compensates it self, and less current flows as it gets warmer, or Vgs is rising.
If one use them as drivers mounted on the same heatsink as the outputs they will shunt down bias as they get warmer.
Swapping them for verticals would cause problems then.
With rising current over drivers bias rises, and at the same time BJT's do the same. Thermal runaway.
Figge
There are propably a lot of experienced people here that do this a lot better than me...
When Vertical fets as well as BJT's gets warmer Vgs and Vbe changes and more current will flow.
Bias network usually compensates for it.
Lateral fets works the opposite way, and sort of compensates it self, and less current flows as it gets warmer, or Vgs is rising.
If one use them as drivers mounted on the same heatsink as the outputs they will shunt down bias as they get warmer.
Swapping them for verticals would cause problems then.
With rising current over drivers bias rises, and at the same time BJT's do the same. Thermal runaway.
Figge
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Something is wrong here. I brought the lateral vs vertical subject in the beginning but been told that the amp has worked for years with vertical mosfet as driver. Since lateral has different pin out than the vertical it is obvious that the pcb is made for vertical and does not match with the schematics shown. Is the pcb a clone attempt or really the original one? Putting a lateral would require to twist the transistors leads...
High power vertical mosfet installed on main big heatsink and operated in low drive current with general proper vbe temperature compensation for the amp could possibly work too and it seems it did for years...however a lateral driver would be a wiser choice but temperature compensation might need to be readjusted if done previously with vertical as drivers..
There are a few things that do not add up...
Fab
High power vertical mosfet installed on main big heatsink and operated in low drive current with general proper vbe temperature compensation for the amp could possibly work too and it seems it did for years...however a lateral driver would be a wiser choice but temperature compensation might need to be readjusted if done previously with vertical as drivers..
There are a few things that do not add up...
Fab
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bottomline is that the sch does not match the pcb, so rule is to replace with what was in there to begin with, if it looks to be original.
looking at it again, the fet is inside the thermal feedbacvk loop so it gets compensated by the Vbe multiplier ckt(q111), so go for the toshiba vfets.
static sensitive handling, i usually wrap some 30awg solid around the leads (shorting bar) for safe handling, assembly, remove before power is aplied.
if the pic shows your assembly correctly, q111,112 can be seen mounted on the HS together.
looking at it again, the fet is inside the thermal feedbacvk loop so it gets compensated by the Vbe multiplier ckt(q111), so go for the toshiba vfets.
static sensitive handling, i usually wrap some 30awg solid around the leads (shorting bar) for safe handling, assembly, remove before power is aplied.
if the pic shows your assembly correctly, q111,112 can be seen mounted on the HS together.
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I guess we are saying the same thing about thermal feedback.
For the shipment of my vertical mosfet they are already in an anti-static bag but already open. I can use also aluminum foil paper for the pins touching each other as others do.
Fab
For the shipment of my vertical mosfet they are already in an anti-static bag but already open. I can use also aluminum foil paper for the pins touching each other as others do.
Fab
looking at the other pic I see white thermal compound and a sil pad.
Not 100% sure but you are not to mix the two.
I only use a very small dab in a corner to hold the pad in position on the HS.
Not 100% sure but you are not to mix the two.
I only use a very small dab in a corner to hold the pad in position on the HS.
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Mica requires thermal compound (drivers in this case) but SIL pad does not (output ). However a very thin small amount of paste has a marginal effect.
Fab
Fab
Just talked with my buddy to get some more info. The schematic has to be wrong. I’ve worked on many amplifiers, integrateds, preamps where the schematic does not match the circuit in the unit (especially Sansui).
He bought the amplifiers from the original owner and does not believe they were ever worked on. He ran them for about a week in stereo and said they sounded great. He then bridged they for two mono amps and has been running them that way for about 6 years. Said they’re the best sounding amps he has had. Unfortunately his Vandersteens have a nominal load of 4 ohms and he stressed the amps.
He said they work in bridged mode, but oddly when he switched it back to stereo the left side fuses went. That’s where I found the shorted outputs. He has never touched the outputs so I can assume they’re factory. The solder joints look factory.
Yes there is a bit of thermal compound on the sil pad. The drivers have mica. The sil pad is one long single piece for all four outputs on the one side. Looks factory.
I’m guessing changes were made throughout the years the amp was made. There are differences in these two amps. Different kinds of film caps, the schematic calls for 15,000uF 80v filter caps and one has that value and the other has 20,000uF 80v Elna caps and they again look completely factory.
I’ve always been in the mindset of replacing what’s in there as long as it looks factory.
Dan
He bought the amplifiers from the original owner and does not believe they were ever worked on. He ran them for about a week in stereo and said they sounded great. He then bridged they for two mono amps and has been running them that way for about 6 years. Said they’re the best sounding amps he has had. Unfortunately his Vandersteens have a nominal load of 4 ohms and he stressed the amps.
He said they work in bridged mode, but oddly when he switched it back to stereo the left side fuses went. That’s where I found the shorted outputs. He has never touched the outputs so I can assume they’re factory. The solder joints look factory.
Yes there is a bit of thermal compound on the sil pad. The drivers have mica. The sil pad is one long single piece for all four outputs on the one side. Looks factory.
I’m guessing changes were made throughout the years the amp was made. There are differences in these two amps. Different kinds of film caps, the schematic calls for 15,000uF 80v filter caps and one has that value and the other has 20,000uF 80v Elna caps and they again look completely factory.
I’ve always been in the mindset of replacing what’s in there as long as it looks factory.
Dan
Attachments
Hey guys, I'm the current owner, and I bought these amps from two different guys, back in March 2013, within weeks of each other. My understanding was that one was the original owner and I honestly don't remember if the second seller was original or second. I try to make habit of only buying from the original owner or second owner, if they enjoyed for years and aren't a flipper. In other words, I like to buy gear from people who respect it and enjoy it. 🙂
These amps have sounded great in mono bridge mode, first with Vandersteen 2C speakers, and then the Vandersteen 3A's. I have NEVER had any performance issues that are audible. As far as I'm concerned, they are a great match. Thanks John C, by the way. Great bang for the buck.
So I can confirm that the amps have never run hot, and never skipped a beat. They have been in service almost daily for 6 years because I work from home, and I listen to music all day.
With that said, I will bet this is the way the factory made them. You may or may not notice that one amp has a serial number sticker and the spec'd 60,000uF Nichicon ps caps on the Parasound site. The second (newer?) amp has a UPC sticker and the serial number appears more to be a typical product id ... and more importantly, the ps caps are upped to 80,000uF Elna.
These amps have sounded great in mono bridge mode, first with Vandersteen 2C speakers, and then the Vandersteen 3A's. I have NEVER had any performance issues that are audible. As far as I'm concerned, they are a great match. Thanks John C, by the way. Great bang for the buck.
So I can confirm that the amps have never run hot, and never skipped a beat. They have been in service almost daily for 6 years because I work from home, and I listen to music all day.
With that said, I will bet this is the way the factory made them. You may or may not notice that one amp has a serial number sticker and the spec'd 60,000uF Nichicon ps caps on the Parasound site. The second (newer?) amp has a UPC sticker and the serial number appears more to be a typical product id ... and more importantly, the ps caps are upped to 80,000uF Elna.
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