Sansui BA-3000 blowing mains fuse following restoration

[richardpp]

Yes, they work well. I have those in the power section of another AU-20000 but with the original drivers and Sanken outputs. I put the in as a precaution to protect the original outputs. I like them.

 

[BradWil]

So you still have the original drivers in your AU20K but do you recommend I change the drivers as a precaution in the BA3K? Pre-drivers already changed.

 

[BradWil]

just checked the specs of the original drivers, they are only 3mhz. For some reason I thought they were much higher speed. Definately want to replace them to err on the side of caution.

What do you think of these repalcements for drivers? @richardpp

2SC1669 (TO220)
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 150 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 175 °C
Transition Frequency (ft): 3 MHz

Replacement MJE15032 (TO220)
Maximum Collector Power Dissipation (Pc): 50 W
Maximum Collector-Emitter Voltage |Vce|: 250 V
Maximum Collector Current |Ic max|: 8 A
Transition Frequency (ft): 30 MHz

2SA839 (TO220)
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 180 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 125 °C
Transition Frequency (ft): 3 MHz

Replacement MJE15033 (TO220)
Maximum Collector Power Dissipation (Pc): 50 W
Maximum Collector-Base Voltage |Vcb|: 250 V
Maximum Collector-Emitter Voltage |Vce|: 250 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 8 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 30 MHz

 

[richardpp]

As mentioned earlier I used MJE15030/1 and MJ211093/4 in combination. They seem to combine well. I have used the amp almost daily for a few years and it's very reliable. You should be fine installing the MJE drivers.

I have another amp (20K) that has NEC drivers and Sanken outputs. I changed the pre-drivers to Fairchild just in case. And I worked on another AU-20K recently where I left both the original pre-drivers and drivers but replaced the outputs. I think once the outputs have been replaced with modern high power devices it changes the game on a couple of levels. For one, preservation is no longer a priority and two, the modern replacements are more resilient.

 

[BradWil]

As mentioned earlier I used MJE15030/1 and MJ211093/4 in combination. They seem to combine well. I have used the amp almost daily for a few years and it's very reliable. You should be fine installing the MJE drivers.

I have another amp that has NEC drivers and Sanken outputs. I changed the pre-drivers just in case. And I worked on another AU-20K recently where I left both the original pre-drivers and drivers but replaced the outputs by necessity. I think once the outputs have been replaced with modern high power devices it changes the game on a couple of levels. For one, preservation is no longer a priority and two, the modern replacements are more resilient.

My apologies, thanks. I only have the 8A MJE15032/33 in stock so will test them out tomorrow.

 

[BradWil]

As mentioned earlier I used MJE15030/1 and MJ211093/4 in combination. They seem to combine well. I have used the amp almost daily for a few years and it's very reliable. You should be fine installing the MJE drivers.

I have another amp (20K) that has NEC drivers and Sanken outputs. I changed the pre-drivers to Fairchild just in case. And I worked on another AU-20K recently where I left both the original pre-drivers and drivers but replaced the outputs. I think once the outputs have been replaced with modern high power devices it changes the game on a couple of levels. For one, preservation is no longer a priority and two, the modern replacements are more resilient.

you mentioned with this combo, the bias was a little out of range of the trimmers - did you need to change the trimmer value or a resistor close by?

 

[richardpp]

Change the value of R20 (1K) as needed. I used 120kΩ resistor in parallel with R20 to give ~990Ω which let me lower the bias to what I needed.

 

[BradWil]

Change the value of R20 (1K) as needed. I used 120kΩ resistor in parallel with R20 to give ~990Ω which let me lower the bias to what I needed.

Awesome, thanks Richard!

 

[BradWil]

Both driver amps as follows:

Pre-drivers KSC3503/KSA1381
Drivers MJE15032/MJE15033
Outputs MJ21196G/MJ21195G

The value of R20 for both driver amps on this unit was 470Ω
The standard value VR02 1KΩ was fine and the amps dialled in perfectly around mid trimmer range

Definitely a great combination of On Semi components, should the original Sanken outputs fail.

I'm confident that the regulated power supply and power amps are now rock solid.

Thanks @richardpp and @Hyperion and others for your help

Driver Amp F-2507 Semis

DES CAT Type Value Volt/LS PWR/hFE RPL Value RPL Volt RPL PWR/hFE
TR01 TRA NPN 2SC1708 DIFF INPUT 412 KSC1845 419
TR02 TRA NPN 2SC1708 DIFF INPUT 389 KSC1845 421
TR03 TRA PNP 2SA847 300 KSA992 490
TR04 TRA PNP 2SA818 94 KSA1381 PINOUT 113
TR05 TRA NPN 2SC1628 111 KSC3503 PINOUT 79
TR06 TRA NPN 2SC945 267 RETAIN
TR07 TRA PNP 2SA733 219 RETAIN
TR08 TRA NPN 2SC1628 PRE-DRIVER 78 KSC3503 PINOUT 83
TR09 TRA PNP 2SA818 PRE-DRIVER 93 KSA1381 PINOUT 119
TR10 TRA NPN 2SC1669 DRIVER 100 MJE15032 103
TR11 TRA PNP 2SA839 DRIVER 102 MJE15033 148
TR12 TRA NPN 2SC984 BIAS 86 RETAIN

Love a happy ending!

 

[richardpp]

Excellent work Brad!

Very interesting that R20 is so different. That will help me understand the changes made to the new board around TR12. Thanks.