Hello Everyone,
I am found quite a bit of discussion around these Sanken SAP 15 N & P Darlington transistors, but I haven't been able to locate anything about my specific problem, so I am throwing it up here to see if anyone has some insights.
I recently purchased a Cambridge Audio A500 integrated amplifier that was working on one channel only. A little bit of research and a quick test on my DMM confirmed that one of the SAP 15 PO transistors was shot and had taken a few resistors with it. (The channel fuses were intact, however.) I decided to replace all four of the Darlingtons and ordered them from ebay. This was a while back, but I noted that the ebay picture was for Sanken SAP 15NO & PO transistors, but the description clearly said SAP 15NY and SAP 15PY. (So mea culpa.) I can't remember now whether I checked to compatibility before I ordered them, but in any case, I replaced the fried resistors (R260 was supposed to be 270R and was around 4M and R258 was 39R in the schematic but when I pulled it, it was a 100R resistor and so was the matching one in the other channel, so I replaced it with 100R) and and checked the bias pots and installed the new transistors. I then attached dummy loads and plugged the amp in. Of course that was an idiotic move - I claim fatigue. Both channel fuses blew.
After installing new fuses and attaching a Variac and dim bulb tester, I can bring it up very slowly, but when the LEDs glow, so do the bulbs. Clearly a large current was being drawn. I have checked the joints and there don't seem to be any bridges at the transistor joints, although a few of them are very tight and I am getting continuity ( around 0.4 Ohms) between the (S & E) 15N pins.
I am hoping that someone out there might be able to tell me if the PO and PY types are incompatible and might be causing this problem, or if something else might explain this issue. Is there a simple way of checking transistors in situ?
Thanks for reading and for sharing any insights you might have.
Andrew
I am found quite a bit of discussion around these Sanken SAP 15 N & P Darlington transistors, but I haven't been able to locate anything about my specific problem, so I am throwing it up here to see if anyone has some insights.
I recently purchased a Cambridge Audio A500 integrated amplifier that was working on one channel only. A little bit of research and a quick test on my DMM confirmed that one of the SAP 15 PO transistors was shot and had taken a few resistors with it. (The channel fuses were intact, however.) I decided to replace all four of the Darlingtons and ordered them from ebay. This was a while back, but I noted that the ebay picture was for Sanken SAP 15NO & PO transistors, but the description clearly said SAP 15NY and SAP 15PY. (So mea culpa.) I can't remember now whether I checked to compatibility before I ordered them, but in any case, I replaced the fried resistors (R260 was supposed to be 270R and was around 4M and R258 was 39R in the schematic but when I pulled it, it was a 100R resistor and so was the matching one in the other channel, so I replaced it with 100R) and and checked the bias pots and installed the new transistors. I then attached dummy loads and plugged the amp in. Of course that was an idiotic move - I claim fatigue. Both channel fuses blew.
After installing new fuses and attaching a Variac and dim bulb tester, I can bring it up very slowly, but when the LEDs glow, so do the bulbs. Clearly a large current was being drawn. I have checked the joints and there don't seem to be any bridges at the transistor joints, although a few of them are very tight and I am getting continuity ( around 0.4 Ohms) between the (S & E) 15N pins.
I am hoping that someone out there might be able to tell me if the PO and PY types are incompatible and might be causing this problem, or if something else might explain this issue. Is there a simple way of checking transistors in situ?
Thanks for reading and for sharing any insights you might have.
Andrew
Thanks, Jon. I'm glad to hear that the transistors should be compatible. They have been installed in the right places, but as to whether or not they are fakes is harder to ascertain. They look identical and the printing is the same. The pins were all untrimmed, so it would appear they are NOS, if not genuine NOS.
You tell a familiar story. I also acquired an A500 one channel down. I could not find any replacement Sankens but built a couple of darlingtons out of discreet power transistors and diodes. They worked but I still had the burnt resistors to replace. I measured the values in the working channel and as you say they were no where near those shown in the schematic. Nor did the values correspond to their markings. I also found the input transistors to be leaking and circuit voltages all over the place. I concluded most of the components were fake and wondered how the amp had ever worked. It's still in bits on my project shelf. I'll be interested in how you get on.
I have five pairs of unused Sanken SAP15's marked NY 9013 and PY 9013. I think I must have had them for over 20 years but I dont remember
what I was going to use them for. They are in a tray with some 2SC2922's and some Semlab engineering sample MAG 2013's s so obviously for
some long forgotten amp project. I can photo them if you are interested.
what I was going to use them for. They are in a tray with some 2SC2922's and some Semlab engineering sample MAG 2013's s so obviously for
some long forgotten amp project. I can photo them if you are interested.
Thanks for your replies, everyone. What you describe, Totally Analogue, is more than a little worrisome. So much for what I thought would be an easy project!
Thanks for the offer, Still Clueless, but I don't know if the parts would be compatible with the internal resistors in the SAP15s.
Zeta 4, I would be very interested in purchasing a two pairs from you if you are willing to sell them.
Thanks,
Andrew
Thanks for the offer, Still Clueless, but I don't know if the parts would be compatible with the internal resistors in the SAP15s.
Zeta 4, I would be very interested in purchasing a two pairs from you if you are willing to sell them.
Thanks,
Andrew
Hi Andrew
OK, I dont think I'll ever use them and its good they could be useful to you, so I'l work out something nominal. I'll will checkout what the postage will be.
Can you pm me where you are ? I'll also send you a photo of them.
Geoff
OK, I dont think I'll ever use them and its good they could be useful to you, so I'l work out something nominal. I'll will checkout what the postage will be.
Can you pm me where you are ? I'll also send you a photo of them.
Geoff
Hello Everyone,
Sure enough, the transistors I bought through ebay were either counterfeit, or defective, or both. I was lucky to be able to purchase a set from Geoff which I installed yesterday. I am delighted to report that the unit is working as it should on all inputs. It sounds really good. Thanks, Geoff! Totally Analogue, you may wish to PM Zeta4 for a new set of Darlingtons and give it a shot!
Thanks again to all of you for your advice and assistance.
Andrew
Sure enough, the transistors I bought through ebay were either counterfeit, or defective, or both. I was lucky to be able to purchase a set from Geoff which I installed yesterday. I am delighted to report that the unit is working as it should on all inputs. It sounds really good. Thanks, Geoff! Totally Analogue, you may wish to PM Zeta4 for a new set of Darlingtons and give it a shot!
Thanks again to all of you for your advice and assistance.
Andrew
That's great news. I eventually abandoned my project as the DC voltages on both channels were unstable.