Radio Restoration

I re-checked that both 2nd local oscillator crystals were starting up ok when the Geloso receiver was cold this morning following my tweaks to their resonant frequencies last night, and both did without any hesitation - good news.
Following a 30 minute warm-up, I re-checked that both crystals were still operating close to their nominal frequencies (they were) and, using the Siglent spectrum analyzer connected to the detector diode plate and feeding a 7MHz signal from an HP8656B signal generator into the antenna jack, that the IF output level was the almost identical on either sideband and on AM - they were.
I then checked that when the BFO pitch control was center-span, there was (approx.) zero beat on both sideband settings (there was), and that a 1KHz tone could be set using the pitch control with a signal tuned in 'on the nose' - it could. The BFO pitch was adjustable to around +/-2.5KHz, so both sidebands could now be properly resolved. I then replaced the chassis into the cabinet and checked that, following my adjustments last night, the RF calibration was still ok - it was, on all bands.
Attached to this post are a number of IF response plots to illustrate the revised response of this receiver now the filter crystal has 'woken up' - they are much better than obtained when the crystal was not well(!). Of course, the crystal could revert to its 'poorly' condition, but I think as long as the set is used reasonably frequently and stored in a warm, dry environment, it should be reliable (time and use will tell!).
That's the great thing about a hobby such as refurbishing/restoring vintage radios - always something new to learn and issues to sort out (or attempt to sort out!).

I've was busy setting up a new laptop plus some gardening jobs most of yesterday, so only limited progress on the Eddystone 830/4.
I installed an IEC socket in place of the 'kettle' connector on the rear apron. The IEC socket was salvaged from an old computer power supply and these, when installed behind the existing chassis cut-out, fit perfectly without any metalwork, with just enough clearance to insert (most) IEC plugs into.
After wiring this in and changing the line fuse to a 2A fast-blow part (a 5A slow-blow fuse was installed!), I made a few resistance measurements between critical circuit nodes and snipped one of the leads of the damaged electrolytic (bypass capacitor in the audio section, so not a critical part). Satisfied that nothing 'untoward' was present after this and a close visual inspection, I decided to try powering-up the chassis slowly (over around 10 mins in approx. 25vAC increments) using a Variac to allow the B+ filter electrolytics to re-form (they usually do ok in Eddystone sets in my experience).
The set 'came alive' at around 95vAC, and was bringing in some stations at the upper end of the Broadcast band (on the lower-end of Band 6), and WWV on 10MHz with a small internal active magloop antenna. All controls seemed to work reasonably well, albeit with some 'scratchiness', and the dial pointer kept sticking around half travel along the dial. At least I now knew the set was viable and well-worth proceeding with the refurbishment.
I then raised the power transformer around 1/4" above the chassis by installing spacers - this to allow improved ventilation (heat convection) of the power supply compartment. This small (reversible) modification is fairly easy to do and makes a lot of difference (all components and wiring in the power supply compartment of this, and most other 830 sets, are really 'baked' and will need to be replaced). I also checked the wiring of the 'Accessory Supplies' plug - it was wired correctly, however, the cover of the Jones plug did not have the usual fishpaper insulation present. As there is B+ voltage in this plug, I decided to install some fishpaper as a precaution. I then wired-up the Jones plug for the speaker (2.5ohm) output, as the jury-rigged internal speaker may have to go(!).
That's all I managed to do yesterday, but this morning I decided to spend some time cleaning the chassis as it was in a rather filthy state - decades of accumulated grime (and I really dislike working on dirty chassis!). First, I removed all tubes - to be tested later - and then removed the tuning gang cover/crystal calibrator unit, and the cover plates from the 2nd local oscillator/2nd mixer sub-chassis. Next I spent best part of 2 hours with Q-Tips, rags and swabs soaked in either 50% IPA, 99% IPA or naphtha to remove the grime from the top of the chassis, antenna tuning trimmer mount/trimmers, tuning gang and its cover. After this, the chassis looks much more presentable, though I will be re-visiting some parts later, eg. the tuning mechanism and tuning gang, for further cleaning/lubrication.