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  1. Greg Stand down in looking for the schematic....

    Greg

    Stand down in looking for the schematic. I did some googling and found the schematic for voltage doubled bias for the 1484 from Gerard Weber’s book. I have installed this circuit and it works...
  2. Hi Greg, Thanks for the info. I had stumbled...

    Hi Greg,

    Thanks for the info. I had stumbled across the documented errors in the schematic - so have been working around those. No problems there.

    I have seen your posts on other forums...
  3. Hi Enzo I follow this schematic that I found...

    Hi Enzo

    I follow this schematic that I found on a 1484 mods website:

    https://www.dropbox.com/s/sp0s2mifp9b0zzu/Photo%2012-11-19%2C%2021%2049%2013.jpg?dl=0
  4. Hi g1, I’ve been using a Eurotubes bias probe...

    Hi g1,

    I’ve been using a Eurotubes bias probe and a fluke DMM. One I’ve had for around 10 years and use to bias all my other amps. Based on this I can get one about 29ma out of the bias pot(50k...
  5. The 50k linear pot arrived today. I didn’t have a...

    The 50k linear pot arrived today. I didn’t have a lot of time to play around today but got it installed and did a little bit of testing and adjusting. Appears noting is ever easy as I found the as I...
  6. Once I receive the pot I’ll install and...

    Once I receive the pot I’ll install and experiment and report back on where I settled in terms of bias.

    In the meantime I’ll recheck the voltage doubler circuit to ensure all connections are...
  7. You’re singing my tune. I’d just ordered a...

    You’re singing my tune.

    I’d just ordered a 50k linear taper pot just for that purpose.

    I’m doing some reading I am lead to believe these amps were generally biased cold from the factory....
  8. Helmholtz Heater voltage is 6.2v and wall...

    Helmholtz

    Heater voltage is 6.2v and wall voltage 122v.

    I’m not too worried - just wanting to be sure it’s all operating ok before I put it back together.

    Noting the 28ma bias - should I be...
  9. Yeah - it is strange. If I take a reading from...

    Yeah - it is strange. If I take a reading from the voltage doubler it is also only pumping out around 450v when it should be 480v. I did replace all the old caps in here with 100uf / 450 caps. Will...
  10. Actually that’s a good point. It presently has...

    Actually that’s a good point.

    It presently has Ruby tubes 6L6GC, which I believe are relabelled Shuguang. I’ll have to look those up as I suspect they are closer to 30 watts. Which would put the...
  11. I thought I would take a closer look at the bias...

    I thought I would take a closer look at the bias for this amp before putting it all back together.

    So noting plate dissipation of 6L6 is 25w and DC plate voltage from pin 3 of power tubes is...
  12. Alrighty So I have attempted to do an updated...

    Alrighty

    So I have attempted to do an updated schematic in terms of how the reverb circuit looks, with some notes, to try and make it easier for anyone who wants to replace the stock reverb in the...
  13. Apologies if I wasn’t clear, but certainly...

    Apologies if I wasn’t clear, but certainly appreciate the input.

    When I get a chance I’ll try the recommended caps and the grid stopper and report back. Almost there!!
  14. Hi Helmholtz Your English seems better than...

    Hi Helmholtz

    Your English seems better than mine!

    Yes - would seem the original schematic that someone drew up for a tranformless reverb was somewhat incomplete. No matter - as working through...
  15. Hi Helmholtz, As Enzo said, the original...

    Hi Helmholtz,

    As Enzo said, the original reverb circuit is a tube driven transformerless reverb. Here is w redrawn schematic of the entire 1484 circuit:
    ...
  16. So tried going straight from the volume wiper....

    So tried going straight from the volume wiper. Didnít seem to like it. Was very noisy (possibly due alligator clips going past tubes and PT but tried to get as much distant between them as I could. I...
  17. Some how I knew you were going to say that! ...

    Some how I knew you were going to say that! Being lazy was avoiding having to do a long shielded cable run to the volume - will grab the alligator clips and give it a test first. Just so happened...
  18. Ah yes - MIs-read ye olde schematic. And yes -...

    Ah yes - MIs-read ye olde schematic. And yes - reverb does play through with volume down - ala original.

    Where would be a good point post volume? Happy to try it.

    Having played it a bit more,...
  19. Hi Harold, Absolutely agree. Iím not...

    Hi Harold,

    Absolutely agree. Iím not necessarily trying to make this amp sound like the previous 1484s I played. When I finally got it working and fired up, I was surprised to find it sounded a...
  20. I have moved the 68k resistor (R58) to its...

    I have moved the 68k resistor (R58) to its rightful home between the 22uf and 10uf power supply caps and all voltages are looking pretty good now. Luckily that was an easy fix.

    Now looking at...
  21. Enzo, Will give your suggestions a shot and...

    Enzo,

    Will give your suggestions a shot and report back. Will seek to simplify the front end and move the input and depth connections and let you know how it goes.
  22. Hi The grids (2 and 7) and cathodes (3 and 8)...

    Hi

    The grids (2 and 7) and cathodes (3 and 8) are tied together. Thatís how I read the schematic and both are jumpered. However separate caps come from each tube pin per the original design. Can...
  23. This is the reverb circuit I am currently using...

    This is the reverb circuit I am currently using for inspiration:

    https://www.dropbox.com/s/nufi88kd1k8ytpi/Photo%207-11-19%2C%2021%2024%2049.jpg?dl=0

    Note I have removed and jumpered R40...
  24. I just checked the power supply caps. The...

    I just checked the power supply caps.

    The circuit looks wired ok - however I did note that one the 68k resistors that bridge the power supply caps was in the wrong place - 20uf and 8uf were wired...
  25. Pin 3 and 8 voltages respectively: V1 - 1.16v...

    Pin 3 and 8 voltages respectively:

    V1 - 1.16v and 1.45v
    V2 - 0.67v and 0.56v
    V3 - 117v and 3.32v

    V4 - 0.69v and 0.9v
    V5 - 7.06v (pin 3 and 8 jumpered)
  26. Hi g1 I played a couple of 1484s a few years...

    Hi g1

    I played a couple of 1484s a few years ago- different room, different guitar. Appreciate there are many variables both internal to the same tube amps, let alone considering the guitar and...
  27. Hi Enzo Thanks for the prompt and detailed...

    Hi Enzo

    Thanks for the prompt and detailed reply.

    Reference the heater voltages, thatís a relief. You are correct - I was measuring to ground and not across the pins. Slipped my mind to measure...
  28. Silvertone 1484 Restoration - almost there, but need assistance!

    Hi All

    First post here, hoping you call help me with what Iím hoping are the last stages of a tube amp restoration. Iíve been lucky enough to be given a Silvertone 1484 Twin 12 piggyback head in...
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