Bringing an Ameritron AL-811HXCE back to life - part 2

So you will recall that this 811HXCE has been badly overheated (to say the least).

I'm pretty experienced on valve amps, grounded grids et al, but i've not ever worked on one of these.

So some internet searching and come up with some nice information and background. I've joined the Ameritron yahoo group (here) (really worth doing a wealth of detail and experience on there) - Also came across a site from a German ham (DC9ZP) who carried out a review (in German) of this sort of amp and had carried out some upgrades (several of which I had planned myself such as a glitch resistor and upgrade HV caps) this site is here.

It really nice that someone has worked and upgraded these before (and thank goodness for google translate!!).

Further research also turned up the guy that designed these for Ameritron and Heatkit - thats Bill  - W8JI.

He has a great deal of stuff about valve amps its a real resource and I strongly suggest if your into this stuff have a look - its here with the specific detail on the 811 series here. It really is great if you (like me) like this stuff !! :)

So I got to thinking about the plate choke (it was burnt out see my previous post) - I Could simply get the parts from the states (UK dealers don't apparently 'hold' spares - difficult to believe i know !!) I priced them up and whilst they are quite low cost (coil at about $30, parasitic board at about $45) the cost of shipping and import duties / VAT would push it up to over £150 - a bit pricey and nearly 2/3rds of what I paid for the amp !

Or I could rebuild them - so I decided to rebuild them (well if they don't work I can also stump up the money !!) - W8JI has a great section on his site about plate chokes (he actually has a picture of one of the ones used in the Ameritron amps !) - here - This gave me the confidence to use the former and wind a replacement - so next post will detail this.

My plans are basically 

1. Work out the wire gauge
2. Mark the former really carefully with where the wire should be (including the gaps !)
3. Count the windings really carefully (at least three times!!)
4. Unwind it (counting the turns to check my counting was right!)
5. Wind on the new wire
6. Seal carefully
7. Measure its resonances using miniVNA

Onwards and upwards !!!!