Hi,
if these are really vertical fets, you will get problems in the circuit (thermal runaway, means self destroying output stage at high power output). The schematics i found from the IBS200 is definitivly designed for lateral Mosfets. For vertical Mosfets with their positive temperature coefficient you have to change the design (temperature compensation)and you need also a vbe Multiplier, due to the higher Ugs of the vertical Mosfets. All in all, as the designed was made for the 2SK134 and the 2 SJ49 from Hitachi, the best way is to replace them by the Exicon types ECF10N20, ECF10N20. You can check this at their home page or take a look on the profusion plc homepage. you get them in different case styles and you are sure that they are really generic.
BR
Günni
if these are really vertical fets, you will get problems in the circuit (thermal runaway, means self destroying output stage at high power output). The schematics i found from the IBS200 is definitivly designed for lateral Mosfets. For vertical Mosfets with their positive temperature coefficient you have to change the design (temperature compensation)and you need also a vbe Multiplier, due to the higher Ugs of the vertical Mosfets. All in all, as the designed was made for the 2SK134 and the 2 SJ49 from Hitachi, the best way is to replace them by the Exicon types ECF10N20, ECF10N20. You can check this at their home page or take a look on the profusion plc homepage. you get them in different case styles and you are sure that they are really generic.
BR
Günni
I tried 1 set of 2sj162/2Sk1058 genuine Hitachi from a new York seller and both were shorted from g-s and d-s. No vom test works and the component tester found them as low value resistors. Looks like seller's revenge for negative feedback.
2SK1058 + 2SJ162 N-FET / 160V / 7A / 100W BY HITACHI | eBay
I'll try the Exicons through a real dealer and to hell with Ebay. Can't trust them any more. It used to work out ok until lately.
2SK1058 + 2SJ162 N-FET / 160V / 7A / 100W BY HITACHI | eBay
I'll try the Exicons through a real dealer and to hell with Ebay. Can't trust them any more. It used to work out ok until lately.
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There are a lot of BJT amps I could switch over to, I really do not see lateral mosfet designs in newer systems. A class D with IFRP verticals could get me quite a bit more watts, out of the same +/- 65 volt power supply. But then it wouldn't be historical.
I held off on the Hitachi TO-3's because I heard they are viciously faked and terrible, been out of production so long, all you get for those are fakes. Unless you pull it from another vintage amp.
I wanted to keep it historical but what the heck, it's not exactly a collector's item like the vacuum tube Marshall amps.
I held off on the Hitachi TO-3's because I heard they are viciously faked and terrible, been out of production so long, all you get for those are fakes. Unless you pull it from another vintage amp.
I wanted to keep it historical but what the heck, it's not exactly a collector's item like the vacuum tube Marshall amps.
Sorry to be the bearer of bad news, I'd rather say what a good supplier I found. Since the lateral mosfet thing is a big crapshoot, and the only Exicon supplier I found is out of 2SK1058's (10N20's) I figure I could run it on an amp module and save the OEM amp module. But that defeats my original plane to see how far it can go.
The seller seems to be honest and does refunds but isn't answering yet. And what a coincidence, another person received a bad set. Maybe I am the only one that has ordered that pair since the last feedback the seller got on them.
I have heard of this fakes thing for years and now I finally get caught up in it.
Can't get 'em from Digikey, Mouser, Arrow, Newark, etc.
I'll have a happy ending story and get Exicons in TO-3's.
The seller seems to be honest and does refunds but isn't answering yet. And what a coincidence, another person received a bad set. Maybe I am the only one that has ordered that pair since the last feedback the seller got on them.
I have heard of this fakes thing for years and now I finally get caught up in it.
Can't get 'em from Digikey, Mouser, Arrow, Newark, etc.
I'll have a happy ending story and get Exicons in TO-3's.
The feedback percentage should have been a red flag. I NEVER order from anyone with below ~99.3% or so.
I just found out I got a full refund. So I'll just wait on a solution. I really don't like a substitute in it. I haven't checked with Marshall, maybe Monday. 2SJ49 and 2SK134's.
Probably extinct.
The new Class D seem to be doing fairly well with a very low parts count, but I like the analog animal. It's a pleasure to work the proportional pumps, valves, and accumulators.
Probably extinct.
The new Class D seem to be doing fairly well with a very low parts count, but I like the analog animal. It's a pleasure to work the proportional pumps, valves, and accumulators.
hi wavewhipper,
the world isn't fair at all.
Imagine, yesterday i bought my second set of unused Exicons (2 pairs 10N20/10P20 TO-3 case) on ebay from a guy from Germany. All in all, it cost me €20 for 4 pairs of them. I checked the first set., and it shows about 600pF for N-channel and 1000pF for p-channel , and the Ugs is about 600mV.
i hope you 'll find the genuine Exicons there in the states.
Good luck
Günni
the world isn't fair at all.
Imagine, yesterday i bought my second set of unused Exicons (2 pairs 10N20/10P20 TO-3 case) on ebay from a guy from Germany. All in all, it cost me €20 for 4 pairs of them. I checked the first set., and it shows about 600pF for N-channel and 1000pF for p-channel , and the Ugs is about 600mV.
i hope you 'll find the genuine Exicons there in the states.
Good luck
Günni
hi,
thats why i stopped, building designs from the past. For my equipment, i most have the power transistors and drivers in storage. I also changed designs for actual semiconductors in production. typical example is the situation for lateral Mosfets. The people won't buy the exicons and search for cheaper stuff on ebay. also have a look at the most wanted JFET 2SK170/2SJ72 GR/BL/V, so much offered on ebay and >95% are fakes, but the people do buy them.
And as long they buy, those dealers make their money. Typical example see this thread. You can't buy 2 pairs of lateral Mosfets for US$10 from a dealer on ebay, when the official price is about 25US$. 2 pairs of verticals costs him about 3 or 4$ and the rest is profit
.BR
Günni
Yes, I know.
Ebay has to be taken with a grain of salt regarding specific stuff, especially when the price is low.
Therefore I wondered if old designs might get an "update" at some point.
Very nice of you "updating" those amps.
But...
I think the sound will inevitably be different/"compromised".
Ebay has to be taken with a grain of salt regarding specific stuff, especially when the price is low.
Therefore I wondered if old designs might get an "update" at some point.
Very nice of you "updating" those amps.
But...
I think the sound will inevitably be different/"compromised".
I decided to go on and modify it for TIP35C/TIP36C but they seem to be headed for the cliff also. Looks like the move is towards the MJL series and I'm totally unfamiliar about them.
I learned to like the TIP's from a Samson Servo 200 general purpose stereo/PA . But it seems sensitive to shorted speaker wires. I had to repair two of them for a guy that lets his 1/4 inch phone connectors get frayed.
I suppose that expensive move to Speakon connectors is also in the plan then not much worry for the unprotected BJT drivers.
I learned to like the TIP's from a Samson Servo 200 general purpose stereo/PA . But it seems sensitive to shorted speaker wires. I had to repair two of them for a guy that lets his 1/4 inch phone connectors get frayed.
I suppose that expensive move to Speakon connectors is also in the plan then not much worry for the unprotected BJT drivers.
No such luck, they were out of the 10N20's in plastic. See the post above, there is my answer. And I should get a few more watts out of a BJT driver because the need less drive voltage swing.
Still having a tough time getting real replacement lateral mosfets. I have some but just by chance they got stuck in the mail, so the lateral mosfet jinx goes on. I think maybe they were meant to be some sort of proprietary device that is difficult to get. Discourages unauthorized repairs and modifications that may affect the reputation of the manufacturer.
That may be what they are protecting. I worked in repair terminals. That division was said to be an expense, not much of a money maker, there for the real intention of maintaining an active product line.
The Marshall IBS200 amp made it 29 years, I'd say a very good product life. I'll probably give up on lateral mosfets and put a more serviceable power amp in it.
What a hassle to that one repair part, but I did learn a lot in the process. Just as with the marginally functional copies and reject parts. But what a hell of diagnosis when every component in your test design is made from inferior Ebay sold parts. You WILL have the need to learn from that stuff. No hard feelings since I learned so much more with the flaky stuff, and I do have a new factory made bass combo amp.
That may be what they are protecting. I worked in repair terminals. That division was said to be an expense, not much of a money maker, there for the real intention of maintaining an active product line.
The Marshall IBS200 amp made it 29 years, I'd say a very good product life. I'll probably give up on lateral mosfets and put a more serviceable power amp in it.
What a hassle to that one repair part, but I did learn a lot in the process. Just as with the marginally functional copies and reject parts. But what a hell of diagnosis when every component in your test design is made from inferior Ebay sold parts. You WILL have the need to learn from that stuff. No hard feelings since I learned so much more with the flaky stuff, and I do have a new factory made bass combo amp.
I'm working on a BJT conversion of the amp. Since I need to add a pre-driver, then I will make most of the mod on a little perf board. These are on order, they look like nice audio power transistors. Did a lot of digging to find them.
MJW3281/MJW1302.
I figure I'll get a few more watts out of this BJT mod over mosfets because this amp does not have a pre-drive boost supply, it all runs off +/- 65VDC.
MJW3281/MJW1302.
I figure I'll get a few more watts out of this BJT mod over mosfets because this amp does not have a pre-drive boost supply, it all runs off +/- 65VDC.
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