Silvertone 1474 &*^%$#

[drewl]

Is it only me who gets Silvertone amps that don't match the schematics?

This one needs a bit of TLC, caps, a good cleaning.
The 6CG7 stage is making some funky noises, probably bad tube as it's loading down the plate voltage, also the .01 coupling caps on the inputs look bad, actually I think a few of those green .01's all over are going bad.

of course the reverb "tube" is bad, might convert it to use a standard tank.silvertone1474.pdf

[Dave Curtis, dB AudioTech]

Silvertone schematic? I think that's an oxymoron. ) Gibson is another amp that rarely matched the schem.

[Enzo]

I was thinking the same thing. Silvertone? Must not have run into many Gibson amps.

[drewl]

Some Gibsons are okay, but all these "low budget" amps look like they were designed by the same guy!

When I used to work on test equipment, we had a running joke that every bad design was probably the same guy getting fired and then moving on to another company.

[drewl]

Okay, went over some things and have this amp mostly working really well except for a couple details.

I can see why they changed the reverb driver to a 6CG7 on other models, not much drive.
I'm going to switch to a regular tank, drive it with a 6CG7, I need to rewire the heaters on the first two tubes there. They're using DC from the output tubes' cathodes which is too high anyway, it won't heat a 12AT7, or a 6CG7.

What's going on with the 3rd 12AX7 before the 6CG7 phase inverter?
Why'd they wire it up like that?
Getting alot of noise there, sounds like the ocean. Need to do the plate resistors and coupling caps.
As I had mentioned earlier, alot of those green .01 coupling caps are leaking, and several 100K plate resistors are bad, they all have to go.

[drewl]

Well so far I rewired the filaments to the first 2 preamp tubes, still not getting as enough drive to the reverb tank, plenty of return.
Anyone convert one of these to use a standard reverb tank?
if you have the circuit, that would save me some time.
Otherwise, I'm going to try a 6CG7 to drive the reverb, I need to rewire for that, possibly like an Ampeg type circuit.
I'm using a standard solid amp replacement reverb tank, 200ohm input Z, 50ohm out.

[olddawg]

If the 1474 is like my 1484, the reverb is pretty useless to begin with. There has been much discussion on this board about these amps, including whether the piezo drive atrocity is technically a tank, lol. From what I understand, it takes a major rebuild to put in a Fender type tank that sounds worth a shit.

[ampdoc1]

I have a couple of 1474s. I finished repairing one a couple of months ago, but wanted a reverb. The existing reverb tube/pan/tank (??) works, but it is awful. No,..yours isn't acting up,...it's truly awful. I had another one of these amps in the early 70s, and it sucked then.

I hunted around for more info, and found one guy who was very helpful, but ultimately I decided that the options would require some re-wiring or an added driver transformer, and I didn't want to compromise the great sound these amps have. Several people suggested a tank (Model #4FB3D1B), but while the spring noise could be heard from the return, nothing I tried would produce enough signal to drive the springs.


Then, a couple of weeks ago I happened to see a 1474 for sale on Ebay. The seller discussed the amp a bit, and revealed that his amp tech told him he could use the amp's reverb RCA jacks as a kinda effects loop. I hurried to the garage and hooked up a cheap Nanoverb. Worked great with the amp.

Unless you know a lot about impedance matching, I'd suggest the "loop" is by far the easiest road,..but a reverb TX should be pretty easy to add.

[olddawg]

I have a couple of 1474s. I finished repairing one a couple of months ago, but wanted a reverb. The existing reverb tube/pan/tank (??) works, but it is awful. No,..yours isn't acting up,...it's truly awful. I had another one of these amps in the early 70s, and it sucked then.

I hunted around for more info, and found one guy who was very helpful, but ultimately I decided that the options would require some re-wiring or an added driver transformer, and I didn't want to compromise the great sound these amps have. Several people suggested a tank (Model #4FB3D1B), but while the spring noise could be heard from the return, nothing I tried would produce enough signal to drive the springs.


Then, a couple of weeks ago I happened to see a 1474 for sale on Ebay. The seller discussed the amp a bit, and revealed that his amp tech told him he could use the amp's reverb RCA jacks as a kinda effects loop. I hurried to the garage and hooked up a cheap Nanoverb. Worked great with the amp.

Unless you know a lot about impedance matching, I'd suggest the "loop" is by far the easiest road,..but a reverb TX should be pretty easy to add.

The 1474 has reverb send and return RCA jacks? The 1484 has a hard wired tiny piezo module.

[ampdoc1]

The reverb on the 1474 has chassis mounted RCA jacks. RCA plugs on one end of a shielded cable run to the hard-wired piezo module. If your's doesn't have jacks, just hack the piezo out and install a 1/4 plug on each if the bare cables. Or if you want to keep the piezo intact, just disconnect the wires and install a new cable inside the amp with 1/4 " plugs to the output. The 1474 and the 1484 reverb sections are almost identical, with both feeding the reverb input after passing thru two preamp stages.

Believe me, this works well and it's really cheap and easy to implement.

[jrdamien]

The reverb on the 1474 has chassis mounted RCA jacks. RCA plugs on one end of a shielded cable run to the hard-wired piezo module. If your's doesn't have jacks, just hack the piezo out and install a 1/4 plug on each if the bare cables. Or if you want to keep the piezo intact, just disconnect the wires and install a new cable inside the amp with 1/4 " plugs to the output. The 1474 and the 1484 reverb sections are almost identical, with both feeding the reverb input after passing thru two preamp stages.

Believe me, this works well and it's really cheap and easy to implement.

Well this is an old thread but I just picked up a 1474 chassis so have to ask a question.

How is a nanoverb working through this circuit? Is the nanoverb plugged into external power?

[nevetslab]

Correct Silvertone 1474 Preamp Schematic & Revised with Reverb attached

Having spent the time to trace the circuits of a 1474 Amp that I was restoring & modifying for a client, I just got the schematic loaded into Multisim 11.0's Schematic Capture. I only drew it out as far as the driver stage and stopped. There are, of course further deviations in the power supply and output stage that don't quite match the actual 1474, but those are minor differences. When I have a little more time, I'll render a complete schematic. But, what I've attached shows what the real preamp circuit is. Multisim doesn't have a symbol for the 6CG7, and I used a 12AX7's symbol so disregard the Pin 9 showing in the heater connections, as that pin is N.C. on a 6CG7.

I'll also render the revised 1474 schematic (when I get that completed) where I used a Fender Reverb Tank Driver Transformer to drive a Reverb. The tank is short Accutronics 82B3C1B triple spring., with it's primary in the Plate circuit of the 6CG7.

1474 Preamp Schematic-1.pdf



I have added the revised 1474 Schematic that has the Accutronics reverb tank & Fender Driver Xfmr type 037099 in the plate circuit of V2 (6CG7).

1474 Preamp Schematic-2.pdf

[drewl]

Wow, that's clean.

Most of these I get in look like they were stored in a barn for twenty years.