11-27-2016, 05:16 PM
Time for an update. Back in Aug I got a replacement osc transformer from Gary @ Playthings but just now got around to installing it. It's got 12 wires going all over the place. Used some numbered stickers to mark all the leads and dug in. After abt an hour it was all wired up and ready to go.
So powered it up a n d it was better but not working properly. Instead of being 400kc off it was only 150kc off. The osc high end adjustment (#29) does nothing and the low end (#16) does a little. I wired up my new toy (digital counter) to the LO output. The cathode of the 76 osc tube provides a good low impedance output though a cap to drive the counter. Now I can see what is going on. At the dial setting of 600kc the LO needs to be at 1060kc (600+460) it was abt 1400kc. That prompted me to add some fixed micas across the low set padder (#16) and got the frequency lower but not enough abt 1200kc w/1100mmfd. And still 29 does nothing. Hmmmmmmm.
While I was cogitating on these problems I though I check my little free Griefkit SG-7 against the counter. At 1600kc it's good (1598kc) but at the low end of the mw band it sucks like 50kc sucks. I think this inaccuracy effected my reasoning as to problem with this osc circuit. I guess I'm gullible!
Speaking of gullible I found why #29 doesn't do anything, in the rider's it not where it sez it is!!!!!!!! It's actually where the POL band adjmt !!!!!! That non working #29 is pretty much what started this whole adventure down oscillator road! D**&&^++#@@@@$=%T!!!!!!!!!!!!!!!!!
As it stands now BC osc is working well and tracking within a few kc. However it wants to die below abt 650kc (I'm thinking the tuning cap has a bent plate or something) Is playing well above 650kc and sensitivity is good too.
Other issues are open shadow meter and spkr vc rubbing. Thought it had a bad volume control as at low volume it had a fair amount of hum in the audio. Ordered a a couple of replacements but now that it's passing good rf and if signals you don't hear the hum at all.
Kinda fun doing the osc alignment using a counter rather than a generator. You can get it right on the money pretty easily. Will probably take a look at the SW bands and do the alignment on them too again.
So powered it up a n d it was better but not working properly. Instead of being 400kc off it was only 150kc off. The osc high end adjustment (#29) does nothing and the low end (#16) does a little. I wired up my new toy (digital counter) to the LO output. The cathode of the 76 osc tube provides a good low impedance output though a cap to drive the counter. Now I can see what is going on. At the dial setting of 600kc the LO needs to be at 1060kc (600+460) it was abt 1400kc. That prompted me to add some fixed micas across the low set padder (#16) and got the frequency lower but not enough abt 1200kc w/1100mmfd. And still 29 does nothing. Hmmmmmmm.
While I was cogitating on these problems I though I check my little free Griefkit SG-7 against the counter. At 1600kc it's good (1598kc) but at the low end of the mw band it sucks like 50kc sucks. I think this inaccuracy effected my reasoning as to problem with this osc circuit. I guess I'm gullible!
Speaking of gullible I found why #29 doesn't do anything, in the rider's it not where it sez it is!!!!!!!! It's actually where the POL band adjmt !!!!!! That non working #29 is pretty much what started this whole adventure down oscillator road! D**&&^++#@@@@$=%T!!!!!!!!!!!!!!!!!
As it stands now BC osc is working well and tracking within a few kc. However it wants to die below abt 650kc (I'm thinking the tuning cap has a bent plate or something) Is playing well above 650kc and sensitivity is good too.
Other issues are open shadow meter and spkr vc rubbing. Thought it had a bad volume control as at low volume it had a fair amount of hum in the audio. Ordered a a couple of replacements but now that it's passing good rf and if signals you don't hear the hum at all.
Kinda fun doing the osc alignment using a counter rather than a generator. You can get it right on the money pretty easily. Will probably take a look at the SW bands and do the alignment on them too again.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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