Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on August 25, 2016, 11:51:50 am
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Hey guys, just had a client ask me if I could build him a Fender Reverb unit in this Old Philco radio cabinet. I have on hand, a Marshall style chassis 12"W x 7"D x 2.5"H that fits in the bottom of the cabinet perfect. Im thinking, mount the tubes vertical and build a shelf in the upper part of the cabinet for a short type reverb tank. If I can swap positions with the input jack and the dwell control it would save me from cutting up the face of the cabinet. I will install an IEC receptacle on the back of the chassis along with a fuse holder and power switch. The only concerns I have is possible hum issues. Any comments or suggestion are much appreciated.
Punky
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I like the idea. Let's see the radio cab.
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Battery went dead in the camera. Its on charge. May take awhile it charges slow.
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Pics of Philco radio cabinet
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more pics
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Ciao Punkykatt
There is plenty of space there to do as Vox do it in the trapezoid cab
(http://i.imgur.com/Uwp6szv.jpg)
May be a thin aluminium foil (as bottom of the amp chassis) can be of some utility, under of this foil you place the plywood panel
Using this method may be you are also able to allign the radio cabinet panel pot holes to the aluminium chassis
Franco
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Franco, thank you for the suggestion. If I raise the chassis to match the upper holes in the cabinet the upper arch will be in the way of the other pots. The way I have it now there is room for two pots, tone and mixer (using small 801 style knobs) under the lower arch on one side a the dwell pot under the other arch. Input and out will be in the existing lower holes.
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Do you have the glass dial plate and push button assembly? If so, I would mount those, put in a piece of old grill cloth, and use the existing four holes for a rotary power switch and the three pots, all with antique knobs. This keeps the look of the old radio. Then put all input/output jacks on rear of chassis.
Here's an old RCA that I did. It may give you some ideas...
http://sluckeyamps.com/RCA/RCA.htm (http://sluckeyamps.com/RCA/RCA.htm)
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If you have the dial glass plate and the push button assembly to mount it is a very good idea, the only I'll do
If you haven't the dial glass plate a possible other way will be to mount the chassis in the upper of the case and use the dial glass plate window to show a faceplate with knobs, on the lower holes you can mount fake pots
Perhaps I don't like so much upside down tube mount
Franco
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I have the dial plate in very bad condition, no push buttons. Chassis is too wide to mount in upper cabinet. If I did try to mount any pots outside of the chassis would that be prone to hum?
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If I did try to mount any pots outside of the chassis would that be prone to hum?
Not if you do a good job.
I would simply bolt a 12" by approx. 6" plate to the front of your chassis. (Think faceplate but it would be about 6" high, not just 2.5" high.) May not need to be 6" high, but needs to be high enough to mount the upper pots so they align with the holes in your cab. You may need to build some shaft extensions like I did on my radio.
This front plate could actually be two 2" x 6" plates (one for each pot). These are just ideas to help keep the original 'radio' look. Use the glass plate even though the writing may be in bad shape. And since the holes for the push button switch assembly are round, you could just put some wooden dowels in the holes to simulate the look of pushbuttons.
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Punkykatt which is the exact model of your Philco ?
and/or which are the measures of the window for the dial plate ?
Franco
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Nice RCA radio conversion there, Sluckey! I had not seen that. Of course, I was stunned to see you re-use those old wafer sockets until the last sentence on your post. I will use them ONLY on some sort of breadboard something that I am scrounging, otherwise they get drilled out and tossed.
Most old CONN organs furnish 6-7 of these aluminum chassis things with 6x wafer sockets. The tubes are upside down and the pins are up, which makes fiddling with the circuit very convenient.
(http://i172.photobucket.com/albums/w32/ttm4/2004-12-31%2023.00.00-7_zpsyse2ssyz.jpg) (http://s172.photobucket.com/user/ttm4/media/2004-12-31%2023.00.00-7_zpsyse2ssyz.jpg.html)
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Steve, There is no glass over the dial face there was this plastic piece (see picture)stapled to the cabinet from the inside. Wow all I need is 2 pieces of 1"x 1" x1" x1/16th"thick alumimium angle pop riveted to the top of the chassis to reach the existing cabinet holes to install the pots. How did you make the pot shaft extensions?
Franco, the model # on the original chassis is:40-146 code 121. Opening in the cabinet is 1 1/4" H x 7 7/8" wide.
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For shaft extensions... I bought four 1/4" shaft couplers from eBay. They have two setscrews that lock on to the pot shaft and then the extension shaft. My extension shafts are about 2" long and were cut from a 1/4" x 36" aluminum rod I bought at Lowes.
Notice the two indicator lamps I mounted on each end of the brown dial back piece? You could probably do something similar. These lamps illuminate the dial but also serve as power on indicators.
I bet if you play around a bit with your dial assembly you can come up with a way to attach it to your new chassis. Hech, your pots may even mount to that bracket?
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Hmmm got me thinking now. I could use that bracket assembly to mount a shelf for the reverb tank too. What are your thoughts on putting led`s in the push button holes?
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As a completely random idea, what if you mount the chassis vertically with the open side facing toward the back? The tubes would be standing up and visible behind some sort of window where the glass tuning scale used to be. The reverb can would be mounted on the floor of the cabinet, in back of the chassis. You'd probably want to fab a rectangle of sheet aluminum to cover the bottom of the chassis box but that is a shielding matter you may well have to address in some format anyway. The pots (and the in/out 1/4" plugs) are mounted in what would normally be the top of the chassis. Paint the top of the chassis and that color shows through the 6 large central holes in the cabinet and the 6 push-button holes. Which means the work to deal with those is done.
I have no idea whether the dimensions would work out, but you could check the overall feasibility in 2 minutes at your end.
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Till now I haven't find an original Dial Plate good image, but the idea is to find something that you can like and modify (with an image program)
the dimensions of the imase as to fit the window of the cabinet
Something like this (that is from one other Philco Model)
Original of one other model
(http://i.imgur.com/UEIDbNe.jpg)
Modified to fit your case
(http://i.imgur.com/widua82.jpg)
EDIT:
I've find this other Dial Plates, not the same of your model but similar
if you like one of this I can remove the orange write on it
tell me if you are interested in one of this
and which are the dimensions of the original faceplate you have
Ciao
Franco
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thanks Franco, i will have to see what the owner wants to do.
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OK, Ciao
Franco
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http://el34world.com/Hoffman/files/Hoffman_6G15.pdf (http://el34world.com/Hoffman/files/Hoffman_6G15.pdf)
Steve, You suggested putting the input and output jacks on the back of the chassis. I will be using Doug`s layout. Where would be the best spots to locate these to avoid any hum? Thanks in advance.. Punky
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Put them on the opposite end of the chassis (hopefully near V1) from the AC cord, fuse, power transformer. That idea was simply to avoid drilling any more holes on the front of that cabinet.
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Thank you.