Standby Switch Wiring in Sentura II

[patlaw]

I'll go ahead and post this picture in case anyone is interested. The Sentura II has the reverb/tremelo board, which makes space a premium inside the chassis. Here's what I came up with to mount new caps for the first and second caps after the GZ34. The terminal strips are mounted on existing screws, so I didn't have to drill any holes in the chassis. The 6.8K 2W resistors were upgraded to 3W versions. They get quite warm even with the correct voltages across them.

One thing I forgot to do was replace the 1uF and 2uF caps in the tremelo circuit (blue circle). They're working, so I may leave them alone, but if I replace them, they'll probably outlive me. Ugh.

[Tom Phillips]

I'll go ahead and post this picture in case anyone is interested...

patlaw,
I thought this was a great thread. I really liked your workmanship, the corrected schematic you posted and your clear high resolution photos.
I'd really be interested in seeing full size before and after gut shot before and after photos if you would care to post them.
Cheers,
Tom

[patlaw]

The power cord is the original two-wire cord. What size wire does the three-wire cord need to be? 18/3? Should I just cut up an IEC computer power cord?

Am I understanding correctly that the three-wire power cord will lower the noise of the amp that the death cap was designed to lower?

[patlaw]

I'd really be interested in seeing full size before and after gut shot before and after photos if you would care to post them.

There are no before pictures. The work that was done before was not really pretty. I'll post a final picture before I button it up. I just got seven new knobs for it from gbono. The next step is to replace the power cord and remove the death cap. Then I have to take the faceplate off to replace the power switch, which I have.

My final challenge is whether to remove the SM-1 photocell and plot a voltage-versus-resistance curve so that I can duplicate it with another device if the SM-1 fails. I found some old LDRs that may work, but I'd have to test them. Taking the SM-1 out without damaging its leads could be a challenge. Things don't always go as planned.

Regarding the SM-1, didn't I see somewhere where someone had done a plot, as above, and created a substitute device for the SM-1?

[Tom Phillips]

...What size wire does the three-wire cord need to be? 18/3?

!8/3 is fine

...Should I just cut up an IEC computer power cord?

That's OK if the cord is long enough for your needs. I like to use 9' cords. Some of the computer cords are only 6' or less. If you cut off the female end I suggest that you ohm out the individual leads to verify that they the colors are connected to the correct pins. I have found serious mistakes inside some of those cords.

...Am I understanding correctly that the three-wire power cord will lower the noise of the amp that the death cap was designed to lower?

It will lower the noise as much as the cap did. However, the main purpose is for safety.

[Chuck H]

I like to use 9' cords.

The longest cord I can get with an integrated plug in the gauge I want from Mouser is 15'. That's the one I use on my amps. Not needing an extension cord on stage is a beautiful thing

[patlaw]

The longest cord I can get with an integrated plug in the gauge I want from Mouser is 15'. That's the one I use on my amps. Not needing an extension cord on stage is a beautiful thing

This one?

EDIT: There are two versions of a 10' power cord at Mouser. One is an SJT (0.315" diameter) and an SVT (0.240") diameter. Since the amp is not where I am, I can't measure the OD of the cord that is there. Since it's a two-wire cord, I'd expect the OD to be closer to the SVT than to the SJT. I don't want to change the Heyco bushing or drill the hole for a larger diameter strain relief. Does anyone know the likely diameter of the existing two-wire cord?

[Tom Phillips]

I can't say for sure what the original SUNN used. However, my guess would be an SVT (0.240" diameter) size. That's what I like to use.

[gui_tarzan]

I like this thread, I have a Sentura II (currently all apart) and a Spectrum II (currently in-progress).

[patlaw]

I like this thread, I have a Sentura II (currently all apart) and a Spectrum II (currently in-progress).

How are your projects coming along? Can you post some pictures?

[gui_tarzan]

They're not, I have too many customer amps to get working first. One of these days...