Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on September 06, 2019, 01:52:14 am

Title: W.H. Paling Amp
Post by: TIMBO on September 06, 2019, 01:52:14 am

Hi guys, Got another resto to tackle. :drool
(https://i.imgur.com/eqcMlU3.jpg)
(https://i.imgur.com/XBRxncG.jpg)
(https://i.imgur.com/3xGtAv0.jpg)
(https://i.imgur.com/FsIqxXp.jpg)
(https://i.imgur.com/PT8s7ng.jpg)
Not a lot of info on this one.....
https://www.ozvalveamps.org/paling.html
The chassis looks mostly original and circuit as well.
Valve line up 6U7GT, 6V6GT and 5Y3..... :hmmmm
I'm in the process of reverse engineering, a couple of the old resistors are not what the colour code is saying and some colour bands have come off.
I'm looking for another circuit that may give some clues but not too many amp has this pentode in the preamp.
Any known circuits that are similar to the valve arrangement out there????

Title: Re: W.H. Paling Amp
Post by: TIMBO on September 06, 2019, 05:44:29 am

Reversed engineered schematic
(https://i.imgur.com/vE6z0hU.jpg)

Title: Re: W.H. Paling Amp
Post by: bmccowan on September 07, 2019, 10:09:58 am

Cool looking amp. I've never run into that pentode, but many early SE 6V6 amps used a 6SJ7 pentode, eh? I imagine you'll be able to work out the resistor values correlating from data sheets. Surely those 100uf caps were recent replacements that are way larger than original. - 8 or 10 being more typical I think.
Find any date codes? I would guess its from the late 30s?

Title: Re: W.H. Paling Amp
Post by: TIMBO on September 08, 2019, 04:05:41 am

Hey Mac, We believe it to be built in the 1940s.
Some info here...
https://www.guitargear.net.au/discussion/index.php?topic=51830.0
It seems the original amp did not have a power transformer.
the valve line up is not like the original.
Someone with a bit of an idea has rebuilt it to the above schematic.
I don't know how long it has been operating with the 100uf caps.
I'm hoping it has not done any damage to the 5Y3.
The original amp had 2x6J7g and 2x 6V6g.
I have not found the specs on the PT to know what it will handle.
I built this for my Cigar box guitar amp...
(https://i.imgur.com/aVEN7Gr.jpg)
(https://i.imgur.com/wi0BYPP.jpg)
Sounds awesome with a real bluzie growl.

Title: Re: W.H. Paling Amp
Post by: bmccowan on September 08, 2019, 08:21:17 am

Ha! What a great pic of that lap steel player. So, that info explains some of the tortured chassis. I like the idea of that cigar box amp - going to look and see if you have a thread on that. I have an old Magna amp that has a 6J7 into a 6SJ7 - kind of strange as except for the grid cap, I think they are the same. I also recently built a Gibson 185 from a Muzak PA; which is an all triode strapped 6SJ7 preamp. Makes for a funky old-timey sound, I think.

Title: Re: W.H. Paling Amp
Post by: bmccowan on September 08, 2019, 08:30:44 am

Found your cigar box amp thread - very cool - love those 6j7g soldiers!

Title: Re: W.H. Paling Amp
Post by: TIMBO on September 22, 2019, 03:48:26 am

Thanks...
Not convinced the circuit as is was worth fixing the multiple problems and recycling the existing parts, the owner was happy to go with my schematic.

(https://i.imgur.com/LtaTBch.jpg)
The chassis striped, sockets cleaned.

(https://i.imgur.com/GQkxt9T.jpg)
Another socket and tag strips added.
Power transformer and output transformer checked out OK

Title: Re: W.H. Paling Amp
Post by: TIMBO on October 07, 2019, 02:42:04 am

Hi guys, This is where I'm at for the moment.
(https://i.imgur.com/Qq4XSQn.jpg)
I have gone through all the resistors that I have and found some that are close to the marked value as well as the circuit value.
I found some Wellwyn resistors on ebay that are on the way from WA, so hopefully there will be something I can use.
Reused the mustard caps from the amp.
In the pic I have rehoused the new Ecaps in some cardboard sleeves from some vintage caps.
(https://i.imgur.com/Qq4XSQn.jpg)
Taking another look I was not convinced the mustards looked right.......
So some more digging into my bucket of discarded caps found the legendary wax caps  :hmmmm
And....
(https://i.imgur.com/Veu4RSr.jpg)
I was able to remove the outer cardboard sleeve and clean the wax off
(https://i.imgur.com/2okzG8p.jpg)
The mustards were placed inside, a bit supa glue to hold it together, hotglue in the ends with black paint over
(https://i.imgur.com/EEP1cjG.jpg)
Clear coat over
(https://i.imgur.com/UmIadwA.jpg)
Spot the fakes  :thumbup:

Title: Re: W.H. Paling Amp
Post by: shooter on October 07, 2019, 07:52:12 am

love the ingenuity you put into these builds!
nice work  :occasion14:

Title: Re: W.H. Paling Amp
Post by: TIMBO on October 12, 2019, 04:17:17 am

Thanks shooter, The amp has fired up well, even a shock to me, no that's not right, I was shocked it worked. :scratch
(https://i.imgur.com/nYXpU70.jpg)
(https://i.imgur.com/uCoz0MF.jpg)
(https://i.imgur.com/WU8lD30.jpg)
(https://i.imgur.com/DaYVjvG.jpg)
I a quite surprised that it has little hum/buzz.
Will get a schem and sound clip asap.
just waiting on a new cloth covered lead to arrive.