SB200 mod for inrush protection

[N2RJ]

One of my friends in 9Y recently purchased a SB200 from a SK's estate. He got a sweet deal, btw and has been looking for an amp for a long time.

He was looking at the mods and wanted to do the inrush protection mod for the filaments with the thermistor.

First of all, is this mod worth it?

Secondly, is the value of the thermistor critical? If push comes to shove I'll order the one he needs from digikey and mail it to him, but I am wondering if he can use locally available parts, such as a thermistor from an old color TV (used in the degauss circuit).

Finally, any other ways to do this besides the thermistor?

Thanks in advance.

[w2amr]

One of my friends in 9Y recently purchased a SB200 from a SK's estate. He got a sweet deal, btw and has been looking for an amp for a long time.

He was looking at the mods and wanted to do the inrush protection mod for the filaments with the thermistor.

First of all, is this mod worth it?

Secondly, is the value of the thermistor critical? If push comes to shove I'll order the one he needs from digikey and mail it to him, but I am wondering if he can use locally available parts, such as a thermistor from an old color TV (used in the degauss circuit).

Finally, any other ways to do this besides the thermistor?

Thanks in advance.
I have had my SP-200 for about 15 years. It's stock and I have had no problems with it. You might mention to your friend , if it has the original filter caps in the PS , they might be ready to be replaced.

[K1OU]

One of my friends in 9Y recently purchased a SB200 from a SK's estate. He got a sweet deal, btw and has been looking for an amp for a long time.

He was looking at the mods and wanted to do the inrush protection mod for the filaments with the thermistor.

First of all, is this mod worth it?

Secondly, is the value of the thermistor critical? If push comes to shove I'll order the one he needs from digikey and mail it to him, but I am wondering if he can use locally available parts, such as a thermistor from an old color TV (used in the degauss circuit).

Finally, any other ways to do this besides the thermistor?

Thanks in advance.
I have had my SP-200 for about 15 years. It's stock and I have had no problems with it. You might mention to your friend , if it has the original filter caps in the PS , they might be ready to be replaced.

As the owner and lover of SB series amps, I HIGHLY recommend this vendor...

http://www.harbachelectronics.com/

[N2RJ]

One of my friends in 9Y recently purchased a SB200 from a SK's estate. He got a sweet deal, btw and has been looking for an amp for a long time.

He was looking at the mods and wanted to do the inrush protection mod for the filaments with the thermistor.

First of all, is this mod worth it?

Secondly, is the value of the thermistor critical? If push comes to shove I'll order the one he needs from digikey and mail it to him, but I am wondering if he can use locally available parts, such as a thermistor from an old color TV (used in the degauss circuit).

Finally, any other ways to do this besides the thermistor?

Thanks in advance.
I have had my SP-200 for about 15 years. It's stock and I have had no problems with it. You might mention to your friend , if it has the original filter caps in the PS , they might be ready to be replaced.

As the owner and lover of SB series amps, I HIGHLY recommend this vendor...

http://www.harbachelectronics.com/

Yep, he's been looking at some of the harbach electronics stuff too. Thanks.

[wd0ct]

It is not necessary. Imo the only mod these may need is soft key - depending on keying relay capabilites of your rig.

[N2RJ]

Well he ordered the soft start from harbach, despite me telling him that it's not necessary.

I think he may also need a pair of tubes as the amp is putting out "only" 400w on 20m. However I think the problem he's having is that the line voltage is too low. When I was there last year I had to jumper my AL-811H for 230v and run it on an outlet designed for an electric range because the line voltage would dip to approx 105 at night. "Normal" line voltage was 110v.

[K1OU]

Well he ordered the soft start from harbach, despite me telling him that it's not necessary.

I think he may also need a pair of tubes as the amp is putting out "only" 400w on 20m. However I think the problem he's having is that the line voltage is too low. When I was there last year I had to jumper my AL-811H for 230v and run it on an outlet designed for an electric range because the line voltage would dip to approx 105 at night. "Normal" line voltage was 110v.

Did you have him tweak the input network as well?

[N2RJ]

Well he ordered the soft start from harbach, despite me telling him that it's not necessary.

I think he may also need a pair of tubes as the amp is putting out "only" 400w on 20m. However I think the problem he's having is that the line voltage is too low. When I was there last year I had to jumper my AL-811H for 230v and run it on an outlet designed for an electric range because the line voltage would dip to approx 105 at night. "Normal" line voltage was 110v.

Did you have him tweak the input network as well?

Good point! I'll let him know...

[N2RJ]

update: I got the harbach mods and mailed it out to him yesterday.

We'll see how it goes.