Having recently restored a CR 32 from 1947 I had a feel to restore another. Although not shown above there is a 2nd half to this unit being the converter/HT generator unit, available as a 6v or 12v option, either work with negative or positive earthed car chassis. This unit has been coated with a rusty red coloured paint that in the sales pictures gave the impression of being a rust ridded unit. But nothing could be far from the truth, once cleaned up the unit was as mink as you can find for a 70-year-old.
the repair
After giving it a good clean I found a PDF of the manual and checked how it all worked. The two units are connected with a 5 core connecting cable, the sort used for vehicle tow bar connecting. Each end had gone thread bare due to the cable being twisted so much over the surviving years. I rewired and re-connected the two units. No HT coming from the output 5 pin socket, I found if you 'link wire' pins 1-4 (8 o'clock and 10 o'clock positions from outside unit) it overrides the on-off switch for testing.)
 |
| Inside power unit (vibrator fits into 4 pin socket) |
The vibrator generates 300 volts alternating current that is fed to the anodes of two diode valve EZ41, in my case had become no emission, so I replaced it with 2 silicon diodes and a power reducing load resistor as the new diodes will produce more HT than needed and this may damage components.
 |
| Ekco CR 117 power unit diagram |
I replaced nearly all the capacitors in this unit, only the warmth from the valve had dried them out over the years, most modern components are much small, so no problem with space. The rubber washers around the vibrator were degraded, so I fitted some foam around base. (this keeps the noise level down)
After all this we now have HT for the radio. The right-hand outer control knob was seized to the fitting and couldn't be freed, so I just disconnected it, it turned light on-or off on the display and wired light permanently on. The dial and control knobs were very dirty and a crack was repaired on right hand knob. (Guy on line selling re-made Ekco knobs for £50 each - horror)
 |
| Controls before tooth brush clean-up |
I lubricated the band switches as best as I could as front can't be removed because of jammed spindle on right.
 |
| Top view inside radio |
 |
| Under view of radio |
 |
| rear view of radio |
The radio was working now, I swapped a few electrolytic's on rear for more volume and the set was now restored. I added all views for people doing more repairs (PDF can be emailed - message me)
 |
| Ekco CR 117 component layouts |
 |
| Audio and detection circuit CR 117 |
 |
| Signal circuit Ekco CR 117 |
Short video added to show the restored radio working again in a 12v battery
No comments:
Post a Comment