Actually, the tube testers at our neighborhood drugstore and one little hardware store both carried “General Electric” signage. Didn’t get into the Sylvnia/ECG components until I moved to “the big city” of Tucson; where I ended up with a jobber account at Elliot Electronics for my “side job” in CB repair. “Anything for a buck” is a hungry college kid’s motto; especially when one has (had) an addiction to team roping. The ECG replacements for for CB final PA transistors has bias requirements that were “just enough different” from the oem 2SC1307’s that they ran like cr@p without some changes. I finally got an account with “RF Parts” (I think that was the name) in Carlsbad. Took a couple-three days for UPS to deliver, but ‘patient’ spent less “tuning and diddling” time on the bench and the pricing for oem was better; so everybody was happy.
I did spend some major dough at Elliot’s for ECG sweep tubes on a Yaesu FT101 Ham rig that was “weak”; amazingly, their 6L6GC replacements were “drop-in”; about five minutes on neutralizing the pair and the owner was ready for his next contest weekend. (Of course, the guy spent the next 2-3 years telling me to study for my Ham license, so I could be “a REAL radio guy”)
Sylvania did put out some pretty good tubes; even in the ECG service replacement line.
Those audio PA part numbers you mentioned in Joe’s deck… my rusty old brain is trying to process, Fujitsu amps?
That is a mighty nice offer Dave. How are those hi-po manifolds treating you?
I’d love for you to take a look at the radio if it is not too much trouble…the radio only cost me $99 so it is not the end of the world if we have to scrap it.
I could ship it your way with a prepaid return tag…
Excellent, it’ll be fun to troubleshoot this on the forum! Why don’t you send it one-way for now, since we don’t know what parts will be needed.
Haven’t installed your hi-po exhaust manifolds yet. Looking to get those fed into a transverse-mounted muffler w/dual-exhaust maybe through a G-type rear valance.
Yes, still at same address. I sent you a PM with my address just to confirm. Plan is to troubleshoot, while shooting pics and documenting the process on this thread. That particular Motorola unit just seems to look so perfect in your 67, have to get it back in service and re-installed!
Joe took me up on on my offer to take a look at this Motorola unit, and sent it to me. Took me a little too long to finally post about it, life keeps getting in the way of having fun with projects!
The video he posted previously in this thread, showed an 8-Track playing with the balance control fully left, then when he rotated the balance to the right all audio went away. Since I dont’ have an 8-Track cassette, I used the AM and FM tuner to confirm this. However, I can replicate this by either cranking the balance to the right, or by cranking the volume with the balance fully to the left. Although there’s no audio coming out of the speakers at this point, both speaker cones are thumping away in an inaudible rhythm (5Hz?)
For some reason I decided to check the voltage input to the power-amp ICs (IC501, IC502, IC601, IC602) and all are around 5.8VDC. Gotta find out why so low…stay tuned!
5Hz at the output should not be possible in a well designed audio amplification system. It should have a high pass filter that blocks subsonic frequencies. I don’t know the solid state world so great but in the tube world that would be accomplished by the use of electrolytic caps on the cathodes of the preamplification stages and potentially the output amp as well if it’s cathode biased.
There are also typically caps used to block bias voltages from passing from one gain stage to the next, though those aren’t electrolytic and are less likely to have failed due to age where with electrolytics it’s a high probability.
The too-low voltages I couldn’t speculate on really, other than checking for resistors in the power supply that have drifted radically in value and messed up a voltage divider somewhere.
