I decided to recap a McIntosh mc2105 amplifier that I've owned for quite a while. It worked when I started, but I ran into a number of existing problems that I was able to fix. I've attached a schematic.
The issue is in the input section, both the circuit board layout and the schematic are useful. Q5 and Q6 are both blown. (I probably caused this myself through testing for other issues.) McIntosh carries replacements. Their original number was 132-506; their new number is 132-255. I ordered four pieces to be on the safe side. The face of the new transistor reads “A1016 G.” I installed Q6 only to discover it didn't work at all. Googling I learned a few things (I think). If I'm right the common identification is 2SA1016; and, the pin-out has changed so that (looking at the flat face, pins down, reading left to right) the order is ECB. If so, then Q6 was installed wrong.
I installed Q5, left channel, adhering to the new pin-out. It functions, but poorly. I used a small, 8ohm, 100 watt, dummy load on that channel. As gain increases the dummy load gets very hot and the transformer starts to whine. All DC voltages on the input board are correct or a little above normal. Signal input voltage to the left channel (test point 1) is correct; however, the base of Q1 does not show any AC voltage. (The right channel Q6 is missing, however, Q2 base shows correct AC voltage.) Q1,2,3,4 all test OK.
The solution seems simple – find the right transistor and install it properly. But at this point I'm at a loss. I cannot let the unit stay hot for any length of time. I'm not sure I've got the correct part, or that I'm installing it correctly.
I'd appreciate any help. Thx
The issue is in the input section, both the circuit board layout and the schematic are useful. Q5 and Q6 are both blown. (I probably caused this myself through testing for other issues.) McIntosh carries replacements. Their original number was 132-506; their new number is 132-255. I ordered four pieces to be on the safe side. The face of the new transistor reads “A1016 G.” I installed Q6 only to discover it didn't work at all. Googling I learned a few things (I think). If I'm right the common identification is 2SA1016; and, the pin-out has changed so that (looking at the flat face, pins down, reading left to right) the order is ECB. If so, then Q6 was installed wrong.
I installed Q5, left channel, adhering to the new pin-out. It functions, but poorly. I used a small, 8ohm, 100 watt, dummy load on that channel. As gain increases the dummy load gets very hot and the transformer starts to whine. All DC voltages on the input board are correct or a little above normal. Signal input voltage to the left channel (test point 1) is correct; however, the base of Q1 does not show any AC voltage. (The right channel Q6 is missing, however, Q2 base shows correct AC voltage.) Q1,2,3,4 all test OK.
The solution seems simple – find the right transistor and install it properly. But at this point I'm at a loss. I cannot let the unit stay hot for any length of time. I'm not sure I've got the correct part, or that I'm installing it correctly.
I'd appreciate any help. Thx
Last edited:
If "A1016G" =2sa1016 the "G" being a different gain from standard --Hfe=280-560 then the legs should read-
B-C-E ----BOTTOM VIEW ! --with the flat facing TOWARDS you ( as you hold it and look at it.
Quote -"the base of Q1 does not show any AC voltage " --you mean no audio signal input ?
IF ---that is the case then you have a short circuit in Q1.
As this BJT requires only 1ma bias with a 50ma MAX any fault condition directly feeding directly back from the faulty BJT would cause a fault to appear.
B-C-E ----BOTTOM VIEW ! --with the flat facing TOWARDS you ( as you hold it and look at it.
Quote -"the base of Q1 does not show any AC voltage " --you mean no audio signal input ?
IF ---that is the case then you have a short circuit in Q1.
As this BJT requires only 1ma bias with a 50ma MAX any fault condition directly feeding directly back from the faulty BJT would cause a fault to appear.
If I read you correctly, then my pin-out should be BCE instead of ECB as, I believed and installed. This would address the symptoms I described. Not sure why Q1 base is not showing ac; a short in the component would explain it. I am going to reposition Q5 and see what happens. If it works, I'll bet the Q1 anomaly disappears. I'll post results.
Thanks, all, for the help.
Just thought, think I'll install Q6 first; that would eliminate the Q1 variable and test just the pin sequence.
Thanks, all, for the help.
Just thought, think I'll install Q6 first; that would eliminate the Q1 variable and test just the pin sequence.
Last edited:
ECB
2SA1016 pnp transistor complementary npn, replacement, pinout, pin configuration, substitute, marking A1016, equivalent, datasheet
el-component.com
2SA1016 pnp transistor complementary npn, replacement, pinout, pin configuration, substitute, marking A1016, equivalent, datasheet
el-component.com
Towers international transistor selector==BCE
German industrial equivalent book used by most of Europe + the UK -ECA.de use =BCE.
Things might be different in the USA.
German industrial equivalent book used by most of Europe + the UK -ECA.de use =BCE.
Things might be different in the USA.
OLD DIY says:
"ECB
2SA1016 pnp transistor complementary npn, replacement, pinout, pin configuration, substitute, marking A1016, equivalent, datasheet
el-component.com"
ECB is consistent with my research, but it seems not to work. I was hoping that BCE is correct as it would address the symptoms. Duncan2 cites "A1016G," which is what it says on the face of the transistor. The "G" being the difference. I've got one new piece left and one that I think is salvageable. They only cost $ 1each, but it takes three weeks to get a shipment from McIntosh.
I now realise that the views shown in several industrial equivalent books I own do NOT view the BJT,s in the views shown elsewhere as regards the 2sa1016 but as those manuals have not let me down in decades I will keep on using them --BCE can be viewed the other way round as--ECB.
As the German electronic nation swears by them and they are an efficient engineering nation and the UK book has the same there is obviously a difference in viewpoint existing world wide as to the actual pictures of the BJT legs I don't think this is going to be resolved .
I can provide the German company email/telephone number for those challenging this highly regarded company.
As the German electronic nation swears by them and they are an efficient engineering nation and the UK book has the same there is obviously a difference in viewpoint existing world wide as to the actual pictures of the BJT legs I don't think this is going to be resolved .
I can provide the German company email/telephone number for those challenging this highly regarded company.
I will now run through my large amount of electronic spares ,many still part of equipment and look for 2sa1016 BJT,s and check them manually ,
it also includes the well known - 2sa1085 and many others all show -BCE --when the FLAT face is towards you.
it also includes the well known - 2sa1085 and many others all show -BCE --when the FLAT face is towards you.
I am holding a -2sc1815 at one time a well known audio BJT it has exactly the same base -BCE when both measured on a TT and using my old AVO MK8 multimeter when the flat side is facing you its- BCE .
Not sure if this is a question. If so, assuming ECB is correct, voltage drops E-B .700, C-B 675.
Just got some new information from a knowledgeable McIntosh source that the common part number is 2SA970, not 2SA1016. Haven't done any digging on that yet.
Slight difference on bias the 2SA970 was the usual input BJT,s of many audio amps for a long time , both are for audio .
Here's a little more information: I located one of the old, blown, Q5,6 transistors. On the face, it reads 056, M512, EBC. I don't have time now, but later today I'll see if I can track this down. I did replace Q6 with the remaining 2SA1016 and got exactly the same behavior as the other channel. Also, I re tested Q1 and found it was getting ac power to the base leg, sorry about the the misinformation - the piece is difficult to get a probe on and I was concerned about damage. Anyway, I think the odds are strong that there is nothing wrong with the unit except locating the correct component. I ordered some 2SA970-BLs from eBay; I'll try them when they arrive. And, hopefully, there is definitive information available on 056 M512. If I can find the correct generic component, I can worry about correcting the bias later. Also, I had a couple of transistor sockets hanging around that I can use for experimenting with pin placement without having to be worried about damage to the pcb. Thanks for helping out.
Last edited:
Q5,6 On the face, it reads 056, M512, EBC. Probably refers to The part number in the
Mcintosh servive manual for Q5,6 132-056 and the M512 is probably the Hfe for matching the gain (sorted by Mcintosh and printing their numbers).
Found it!
Mcintosh semiconductor data.
http://www.tubebooks.org/file_downloads/McIntosh/semiconductor_data.pdf
From
McIntosh service data
Says that the 132-056 is a 2N5087 on page 8
Mcintosh servive manual for Q5,6 132-056 and the M512 is probably the Hfe for matching the gain (sorted by Mcintosh and printing their numbers).
Found it!
Mcintosh semiconductor data.
http://www.tubebooks.org/file_downloads/McIntosh/semiconductor_data.pdf
From
McIntosh service data
Says that the 132-056 is a 2N5087 on page 8
Last edited: