Acetone 301 help

Discussion in 'Amp Tech Center' started by Steve77, Jul 14, 2020.

  1. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    E43F0DEB-F8A1-415D-9F81-1235A5A558C4.jpeg BE0C2E01-2E35-49CD-A7D6-F59F23E86F83.jpeg
    I know this amp has popped up once or twice in the past. It’s a bit of an odd ball I think. It has an odd, super impossible to find 50hb26 power tube. Fortunately for now that’s not my issue. Maybe later.
    To start, I’m trying to add in a three prong power cord. The layouts a little strange to me. It’s a two prong cord of course. But no death caps at all, which worries me a little. The power tranny wires are not colours I’m used to.
    I drew it out. Hope it’s legible. And I’ll add a pic too.
    Any ideas??
     
  2. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Truthfully was half tempted to just put the three prong cord in just like the two prong cord in there, but with the green to the chassis.
    Bad idea?
     
  3. Jon Snell

    Jon Snell Tele-Meister

    Posts:
    394
    Joined:
    Aug 31, 2015
    Location:
    Jurassic Coast. UK.
    Use a three core mains cable wired as is and the additional Earth wire connected to the chassis. There are a couple of handy holes to the lower left side of your photo. Ideally the Earth should be crimped to a eye tag and then bolted to the chassis using a shake-proof washer in the fixing.
     
  4. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Would it make sense to run the hot(black) to the fuses then to the switch. The yellow orange and pilot light wires on the other side of the switch.
    The neutral(white) connected to the white tranny and other side of the pilot light? really I suppose it achieves the same thing but send a the hot through the switch.
    not sure it makes any difference.
     
  5. Wally

    Wally Telefied Ad Free Member

    Posts:
    35,999
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Steve, I am just having my wake up cup of tea and am curious about this one. Odd arrangement it is. I would put a meter on those wires....What do you see measuring between the three PT leads...white, yellow and orange? White to yellow, white to orange, yellow to orange?
    It would be preferable to fuse the hot before it goes to the switch, but it is an odd situation ime.
     
    rangercaster likes this.
  6. rangercaster

    rangercaster Poster Extraordinaire

    Posts:
    7,561
    Joined:
    May 8, 2008
    Location:
    Knoxville TN for now
    Looks like a simple circuit to me ...

    But I don't know anything ....

    Wally does ...
     
  7. Wally

    Wally Telefied Ad Free Member

    Posts:
    35,999
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    using a balancing scale with what I know on one side and what I don’t know on the other, the “don’t know”side very much outweighs
    The “do know” side. In this case, metering those leads might shed some light. The power tube designation indicates that this amp is based on what some call the American 5 design....the other tubes are 35– and a 12A—, correct. If so, that PT is an isolation transformer. Such a transformer usually has two primary leads and two secondary leads. wall voltage in and the same voltage out with the air gap providing the safety barrier.
    I have no experience with this particular amp and am not understanding. I would have to have it in front of me to grasp what is going on there.
     
  8. rangercaster

    rangercaster Poster Extraordinaire

    Posts:
    7,561
    Joined:
    May 8, 2008
    Location:
    Knoxville TN for now
    I just eyeball the layout ...


    Then I bring it to my tech ...
     
  9. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Wally, that’s a great idea. I left the power cord alone for a bit while I swap out the caps. When I first powered it up the power tube looked to be red plating. Being a rather impossible to find tube I wanted to sort out the old caps before I moved on. As soon as I get the caps switched out I’ll test the power transformer wires to see what’s what. From other amps I’ve seen it does seem somewhat standard to run through the fuse first, but the way this ones done, in that area is a little awkward. I’ve never seen an amp with two fuse for the PT, though I’m pretty amateur.
    I had to order in a 10mfd non polarized cap. Was a little tough to find around here. Seems like anything over 1mfd non polar is a little tough to come by.
    As soon as it shows up, I’ll report back with some PT wire measurements.
     
  10. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Rangecaster, I think your right. The circuit it self doesn’t seem to be too complex, just an odd way of doing it in a few places, but nothing a few new caps and power cord won’t help!
     
  11. Wally

    Wally Telefied Ad Free Member

    Posts:
    35,999
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Steve, ime, the time to meter those windings would be with the filters fully drained if not disconnected...or before powering up the with new filters. What is the entire tube complement? How many secondary leads from that PT? This is one that I would have to understand on some level all of the aspects...to the point that one could draw the schematic by the time that understanding occurred.
     
  12. elpico

    elpico Tele-Afflicted

    Posts:
    1,017
    Joined:
    Sep 14, 2011
    Location:
    Vancouver BC
    It's quite common for power transformers to have more than two leads on the primary. It's usually so the same off the shelf transformer can work for a variety of input or output voltages. If that's how this one was connected before I'd agree you should just do it the same way with the new cord. I wouldn't be worried enough about the switch being on the white to change it but you're the guy who has to work on it.
     
  13. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Ok so my last Cap finally came in. Puerto Rico to Canada for one Cap. All Caps and a couple of resistors now changed. Two new 12ax7s. Fired it up and it does play. A little bit of hum. The hum is always there with or without guitar/cable plugged in or volume on zero. It does get louder as the volume is turned up. On the bright side the power tube does not look like it’s red plating anymore.

    I sorted the new power cord and decided to just wire it in just as it was before, but with the green to the chassis. As for the fuses. On the chassis near the fuses it actually says 100v and 117v. So as I’m in Canada I’ll use the 117 side. I guess it was done to be able to be used in China and North America.

    The tremolo works great but no reverb. I’ll have to dig into that one. The tank might be toast.

    I took some measurements off the heaters. The power tube is right at 50 as it should be. The two 12ax7s though are sitting too high. Actually twice the amount they should be, at 12.5ish vac each. I’m going to go out on a limb and guess this is where my hum is coming from. I’m a little lost on this one. The power for the preamp heaters get it from a tap off the tranny directly. Haven’t even touched that area of the circuit. Did preamp tubes run hotter in the 60s?

    Weird that it’s perfectly twice the amount. There’s something to that.

    The wiring for them is different then I’m used to as well. Only one wire off the tranny to the first preamp heater tab, the second heater tab runs to the the second preamp tube heater tab then the other tab to ground? I’m guessing that puts them in series? Could this be where the double the amount is coming from? Strange though. This is the original wiring.

    Any thoughts guys? I’m so close.
     
  14. Wally

    Wally Telefied Ad Free Member

    Posts:
    35,999
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    100volt power supply...is that not a Made in Japan amp? Okay.l.had to do some quick search....
    https://en.wikipedia.org/wiki/Ace_Tone

    interestingly there is a connection to the Roland Company.
     
  15. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

    Posts:
    1,405
    Joined:
    Dec 30, 2019
    Location:
    california
    Is it hooked up to just pin4 and pin5? That would be correct for a 12.6V heater supply on the 12a_7 type.

    (12 of 12a_7 designates the heater voltage.);)
     
    Wally likes this.
  16. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    Ahhhh, I just did a bunch of searching and wiring diagram comparing. Yes it is hooked up only to 4 and 5. I’ll include some pics. Shortly. I had no idea that is normal for 12.6vac filament wiring. I had never seen it before. unfortunately takes away the cause of my hum, but explains the voltage.
    Thank you!
     
    Lowerleftcoast likes this.
  17. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

    Posts:
    1,405
    Joined:
    Dec 30, 2019
    Location:
    california
    Is there a heater center tap either from the PT or an artificial one? Can you elevate it?
     
  18. Steve77

    Steve77 TDPRI Member

    Posts:
    61
    Joined:
    Oct 17, 2013
    Location:
    Thunder Bay
    I had thought the same and will try. the way they built the amp has some things elevated and some, including the heater wires glued to the chassis. I’m not sure the preamp wire will stay elevated. It’s just a thin, single wire. I may have to Macgyver something. I’m wondering if the hum is coming from the power tube. It’s original. Unfortunately it’s not easily replaced.
    I have read that it can be replaced with a 6L6, but will need a new tube socket and filament transformer. As it’s will inevitably need to be changed, and might be the cause of my hum, I’m tempted to just do it.
     
  19. tubegeek

    tubegeek Friend of Leo's

    Age:
    59
    Posts:
    2,427
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    The suggestion of "elevated" is meant voltage-wise, not physically.

    EDIT: You can't use an elevated heater center tap with your amp.

    Your amp uses a series heater string like an All American 5 radio. All the heaters are connected together in a series circuit and their total voltage is probably 115V. Pull one tube and they all go dark, like Christmas tree lights. The tipoff is the "50" in the tube number.

    If all it has is the 50BH26 and two 12AX7's, that would total 74V and that doesn't make sense to me - are there any other tubes?


    What I said below may be useful BUT NOT FOR THIS AMP.

    Heaters usually are fed an AC voltage, in your case, 12.6 V AC. If the heater center tap is referenced to 0 V, that's going to vary between -6.3 and +6.3. If it's referenced to the cathode of the 6L6 that's at 20V or whatever, it'll vary between 13.7 and 26.3, and this modification can reduce hum from the heaters. (The exact numbers are an oversimplification, ignoring the difference between peak and RMS voltage. Don't worry about it.)
     
    Last edited: Aug 2, 2020 at 8:29 AM
    Wally likes this.
  20. tubegeek

    tubegeek Friend of Leo's

    Age:
    59
    Posts:
    2,427
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    @Steve77 - have you found a schematic for this amp? I haven't been able to so far. @Wally ? Bueller? Anyone?
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.