Silvertone 1483 with shorted OT, need replacement! Help!

[bw1985]

Hi all,

My Silvertone 1483 has a partial short on the primary side of the OT. Not good! But I want to take this opportunity to replace it with something better.

Does anyone have the specs on this OT? I know Mercury has a direct replacement, but its just too expensive. I don't care if it sounds exactly as it was, as I purchased it in its current condition.

Could I buy the Weber 1484 OT and stick it in there? Or is there a better option? Any advice would be appreciated!

Thanks!
-B

[Helmholtz]

My Silvertone 1483 has a partial short on the primary side of the OT.

Are you sure about the short?
How did you test it?
Could you post a schematic?

[bw1985]

Are you sure about the short?
How did you test it?
Could you post a schematic?

The push-pull primary side measured to be 250ohms - 100ohms. Should be 250-250.

Here is the schematic for the amp. It uses 2x6L6 but probably more suited to 2x6V6, I believe similar output power to a Deluxe.

[Helmholtz]

The push-pull primary side measured to be 250ohms - 100ohms.

Ok, that looks wrong. Schematic says 230R-230R. DCR asymmetry up to 25% is normal.

This OT should work fine: http://www.hammondmfg.com/pdf/EDB1750S.pdf (don't know about the footprint).

A bigger core OT like the Weber may increase output by less than 2W. Sound mainly depends on primary impedance.

[Mick Bailey]

I'd also choose Hammond. If you decide to go with 6V6 then you can either go Tweed Deluxe or Deluxe reverb as well. Here's a handy quick reference I use;

http://www.bluebellaudio.com/guitartransoutput.htm

[SoulFetish]

I would personally stay with 6L6s, and upgrade the replacement OT if needed.
But, if you did switch to 6V6s, you're going to want to consider a couple of things - assuming you're going to keep the same plate and screen voltages:
At those voltages on the plate and screens, a 10k p-p load on the primary should keep the tubes from over-dissipating. So, loaded with 10k, if you set the grid at -22V with respect to the cathode, you should get a quiescent plate current of around ≈ 24/25mA (49-50mA for both). If the tubes share the cathode resistor, then -22V/49.5mA is about 440. This would require a change to the value of the stock cathode resistor value from 270Ω to 470Ω, nearest standard value.
At this bias setting, and operating with a 10k load, you should get around 17¹/₂W max output, while keeping you actual plate dissipation under 14W well into clipped signal drive.
This is good, because those 6CG7 are probably going to slam the grids with upwards of 60V peak to peak and turn you into Rock'n Roll McGee

[Helmholtz]

Does anyone have an explanation for the inductor (CH1) wired across the speaker? It can't mean a typical speaker field coil as these require constant DC.

[Enzo]

Bass rolloff. Stops big bottom end from flapping the cheap light weight speakers.

[SoulFetish]

Does anyone have an explanation for the inductor (CH1) wired across the speaker? It can't mean a typical speaker field coil as these require constant DC.

I was wondering about that early

[Helmholtz]

Bass rolloff. Stops big bottom end from flapping the cheap light weight speakers.

Thanks, Enzo. Makes some sense. I guess it will mainly protect the speaker from excessive cone excursion at its bass resonance.

[Chuck H]

Thanks, Enzo. Makes some sense. I guess it will mainly protect the speaker from excessive cone excursion at its bass resonance.

A detail some designers miss. Some coveted amps characteristic sound is relative to how the DEFICIENCIES in the circuits and materials compliment each other. ie: "I built a clone of an (X) amp and the bottom end is flabby." etc.

[Helmholtz]

A detail some designers miss. Some coveted amps characteristic sound is relative to how the DEFICIENCIES in the circuits and materials compliment each other. ie: "I built a clone of an (X) amp and the bottom end is flabby." etc.

True, indeed.
That's one reason why I care about (odd) details especially if the amp sounds good. (Also a technically better solution often spoils the original sound.)
But I'm not familiar with Magnatone/Silvertone/Sears amps, never see them over here.

[g1]

(Also a technically better solution often spoils the original sound.)

This is one of my beefs with the whole mercury mag. 'upgrade' marketing scheme. Better specs. does not necessarily mean it will sound better, or even sound like the original.
They go to great lengths to convince you how the OT is critical to the sound, then try to sell you on an OT that is different than the stock unit?

[Justin Thomas]

I don't recall who, but a few years ago someone started a thread about the Bassman 100 OT being replaced with a TR OT & it got better. Ensued a long discussion about how "bigger is better for bass, but probably only to a certain point..."

I can indeed verify that a BM100 OT is about 2x bigger than a TR OT... No I am not swapping one for the other in my Bassman 100.

Justin

[Chuck H]

I don't recall who, but a few years ago someone started a thread about the Bassman 100 OT being replaced with a TR OT & it got better. Ensued a long discussion about how "bigger is better for bass, but probably only to a certain point..."

I can indeed verify that a BM100 OT is about 2x bigger than a TR OT... No I am not swapping one for the other in my Bassman 100.

Justin

Well in this case it might be more of a subjective opinion as to which is better. If you like the bigger bottom then the stock OT is good for you. Likewise, some might like the Bassman 100 OT in a TR.?. I'm thinking more about something like, say, a 5e3 OT. Suppose you swap that out for a bigger one. Now you get to hear all the stuff the stock (and somewhat fragile I've read) OT was filtering. A lot of guys try to get more oomf out of their 5e3 build by including a larger OT and it usually results in tone anomalies the stock amp doesn't have. The 5e3 is a popular amp for cranking. It uses relatively few gain stages, a lower loss tone stack and a split load inverter. Too much gain too fast doesn't sound as good as some more graceful designs and the cathodyne inverter isn't exactly known for it's good overdrive tone. But somehow in the 5e3 with both those features it works. Until you put in a bigger OT.