philly amp info needed

[mike hadley]

I recently purchased this philly amp from fleabay, I am 99% sure that it is the one Ben Hase had a while back, the one with jones sockets fitted,

most appears to be original and ties in with the schematics available, choke dc resistances measure ok, the four 6l6's all have the correct value resistors to the right tube pins, all match with the philly schematic's

unfortunately the elves have bee busy with this one,

the -27v rail cap has been wired wrong, with the center tap of the power transformer wired directly to chassis, easy fix,

the caps above chassis two seem to be original, the third has a 1971 date code and appears to be a split type cap, 50 - 50 uf, with both sides used, is this the correct type of cap here ie. split, all but the wrong value,

as the wiring is a little messy and no old solder to give any clue, it would make sense as the early philly chassis has four caps in this location.

Someone has been busy around the 10 way jones socket (speaker connection). lots of fresh solder with some evidence if the wiring been moved, although there are the appropriate connections, field coil, 6l6 anode connections etc.

Also there is something really odd with the fuse holder, one side is wired to ac input, through the fuse to pin 10 on the ten way jones socket via a twisted pair,

the other wire in this twisted pair is connected to pin4 on the (radio chassis) 12 way jones connector, this then leads to a single tag mounted on the chassis near the ac input,

was this for the motor option?

a schematic for this later supply would really help as I would like to put things back to factory,

here are some photo's

jones sockets

-27 v supply cap

10 way jones

12 way jones

loose cap

fuse holder

odd cap

Thanks in advance for any help.

Mike

[mike hadley]

Scott,

Can you please email the pictures of the underside of your chassis,

I have decided to fit UNL6W30K-F caps, they are 30uf 600v polypropylene, 5 off

three on top and two underneath mounted horizontally on a steel plate,along with the -27v rail cap,

this I think will allow a sympathetic modification to the chassis,

I will use the existing back rivet holes that c1 and c4 occupy, as these rivets will be replaced with screws from the new capacitor clips, and the plate will sit on a couple of spacers,and will avoid drilling any holes.

There is enough thread from the choke mounting screws to allow two spacers that will give four point fixing of this plate,

this will bring the chassis to the early version schematic, but with jones connectors, not an ideal solution but a working one nevertheless

Mike

[Scott Seickel]

Joseph, thanks for that info.  I am going to order a couple of those switches. 

Mike, why polypropylene filter caps?  I can't think of a single good reason to spend such a large amount of money on a filter cap. 

I wouldn't sweat the amp/PS modification.  It is so hard to find an unmolested unit these days.  I have 3 of them that I am trying to make one out of that is completely original.  I will then have a second one that is mostly original, and a 3rd that will be quite molested.  There always seems to be missing original components on these. 

Do you want pictures of a late model amp/ps or an early one?  Only reason I ask is because you stated that you were going to wire this like an early one. 

[mike hadley]

Scott,

It just so happens that I already have the caps, they were removed from some three phase filters that we scrapped at work a while ago, so they cost nothing, fit and forget.

as for the photo's can I be greedy and have both.

thanks

Mike

[mike hadley]

The amplifier is now complete, I removed the old caps from the chassis, the 100uf cap across the -27v rail was wrapped in cardboard and black insulation tape, not ideal,

the clip was removed and retained for the Ht decoupling cap on the 6l6's.

The caps I have used are 30uf 600v polypropylene, yes a little excessive but they were free,

the three above chassis caps were fitted with standard hardware,

A steel plate was made to hold the other caps under the chassis on spacers,

the cap clip that holds the two black caps was made from steel packing strap, bent to shape and drilled, the steel plate they are mounted on is 1.2mm thick.

The 100uf cap for the -27v rail is under this plate mounted with a single 'p' clip, this cap is an Elna "peg124" type, these are not cheap but as I saved on the main caps I thought that this range would be a good choice,

this type was also used for the 6l6 decoupling, 22uf 450v.

the plate is then mounted under the chassis on four 3/4" spacers, two from the Ht choke mounts and two from the above chassis cap clips,

this is the neatest way I could thing of mounting the extra caps, the best part is the original wiring is retained, and is also reversible,

the two 0.1uf were leaky and replaced,

one of the 240k resistors under the 6l6 tubes was nearly 700k, so metal film resistors are fitted here,

the next step is to make an adapter box to replace the missing speaker and field coil, the psu can then be run up into suitable resistors to check all is ok, before plugging in the radio chassis.

[Joseph W Strickland]

I like the symmetry of the arrangement. It follows the original symmetry of the overall layout. It looks nice and neat. You are doing a great job.

Joe