This questions specifically involves the S5151 and S5151R which are dual diode devices with either common cathode or common anode and the pair are used in many vintage pieces of equipment to rectifier the AC coming from the secondary windings of the power transformer. In all the years I have been doing this I have read, been told that they are 5A diodes. In a pretty much identical case is the SS3 and SS5, the SS3 being rated for 3.5A and a smaller version of the package and the SS5 being rated 5A and the same size as the S5151. Unfortunately there are no data for the S5151. There are some threads I came across where members were asking about changing these out with discrete components and members like Echowars and Avionic which definitely know their stuff recommended 5 amp diodes as replacements like the HER504.
So I showed my replacment of these dual diode packages using MUR550 as I wanted ultrafast soft recovery diodes in place. They are 5A 570v rated. There is one full bridge for each channel of amplification on a Pioneer SX-1250
It was then brought up by another member, I won’t call him out (hopefully he’ll respond here, but he too knows his stuff as well), that the S5151 may not be 5A rated. He brought up the fact that the SX-1050 uses a 20A rated rectifier, so 10A per channel for less output power. So why a smaller rectifier for more power? I suggested that the rectifier may have been overkill, they could have put a 30A or 40A in there.
I then brought up the fact that the SX-950 which is 85 watts per channel, so 170 total (10 more watts total than each channel of the SX-1250) used a quad of the SR3AM diodes, both channel share the one bridge rectifier. The SR3AM is rated for 2A continuous or 3A with a heatsink which they didn’t use.
He then brings up a conversation that he was having with someone wanting to use 1N5404 (3A rated) in the SX-950, but he felt they weren’t adequate and recommended the need for 6A rated diodes. Why would an amp that came from the factory and has been working for nearly 50 years on 2A rated diodes (3A with heatsink) need 6A? The SX-950 runs at lower rail voltages than the SX-1050 and SX-1250.
So I figure if the SX-950 can make 170 watts output using 2A (3A with heatsink) diodes why can’t the SX-1250 make 160 watts using 5A diodes? I’m still convinced that these S5151 devices are 5A. I set up the bride rectifier so that I could measure the current in the SX-1250 and into clipping the amp heavily the highest I saw was a little over 900mA, but of course I wasn’t seeing peaks.
Regardless I put the SX-1250 back together with these new 5A MUR550s installed and it’s been playing for over 24 hours straight, blasting it pretty loudly during the daytime hours playing into my ADS L1590/2 and ESS AMT 1B. They may not be the most demanding load, but it’s been perfectly fine.
But for me it’s down to the fact the SX-950 makes slightly more power total on a lower current rated bridge rectifier and that for as long as I can remember the original has always been thought to have been a 5A device.
Thoughts?
Dan
So I showed my replacment of these dual diode packages using MUR550 as I wanted ultrafast soft recovery diodes in place. They are 5A 570v rated. There is one full bridge for each channel of amplification on a Pioneer SX-1250
It was then brought up by another member, I won’t call him out (hopefully he’ll respond here, but he too knows his stuff as well), that the S5151 may not be 5A rated. He brought up the fact that the SX-1050 uses a 20A rated rectifier, so 10A per channel for less output power. So why a smaller rectifier for more power? I suggested that the rectifier may have been overkill, they could have put a 30A or 40A in there.
I then brought up the fact that the SX-950 which is 85 watts per channel, so 170 total (10 more watts total than each channel of the SX-1250) used a quad of the SR3AM diodes, both channel share the one bridge rectifier. The SR3AM is rated for 2A continuous or 3A with a heatsink which they didn’t use.
He then brings up a conversation that he was having with someone wanting to use 1N5404 (3A rated) in the SX-950, but he felt they weren’t adequate and recommended the need for 6A rated diodes. Why would an amp that came from the factory and has been working for nearly 50 years on 2A rated diodes (3A with heatsink) need 6A? The SX-950 runs at lower rail voltages than the SX-1050 and SX-1250.
So I figure if the SX-950 can make 170 watts output using 2A (3A with heatsink) diodes why can’t the SX-1250 make 160 watts using 5A diodes? I’m still convinced that these S5151 devices are 5A. I set up the bride rectifier so that I could measure the current in the SX-1250 and into clipping the amp heavily the highest I saw was a little over 900mA, but of course I wasn’t seeing peaks.
Regardless I put the SX-1250 back together with these new 5A MUR550s installed and it’s been playing for over 24 hours straight, blasting it pretty loudly during the daytime hours playing into my ADS L1590/2 and ESS AMT 1B. They may not be the most demanding load, but it’s been perfectly fine.
But for me it’s down to the fact the SX-950 makes slightly more power total on a lower current rated bridge rectifier and that for as long as I can remember the original has always been thought to have been a 5A device.
Thoughts?
Dan
Right, I have some, but I was wanting to use ultra fast diodes. I have higher rated diodes, but I’m wondering about the originals and using 5A to replace them as they are 5A themselves.
Dan
Dan
Bumping this to see if anyone else has any opinions on my thoughts of the SX-950 being okay with 2A diodes and the SX-1250 having 5A diodes.
Dan
Dan