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Post by harryorgans on Sept 11, 2021 22:14:36 GMT 12
Hi, new Member here. I play guitar in several bands and a couple of months ago my Fender valve amp died. I took it to be repaired and was told it was going to be a long, long wait as Fender NZ is hopeless with technical support and parts. So I took the amp back and decided to fix it myself, and at the same time, improve on a couple of shortcomings. But before I tackle that project, I wanted to start somewhere simple and got very interested in valve radios on TM. Next thing I knew I was reading schematics and tube data sheets and now I've bought a Bell Colt with the intention of turning it into a compact valve amp suitable for practice or low volume recording. ![]()  Of course this may be utterly sacreligous behaviour, but I figure at least (a) it will be used, rather than sit on a shelf and (b) I'll learn a thing or two. I also figure that the Bell Colt seems quite common, so at least I won't be messing around with something rare. I intend to update this thread with progress and ask lots of questions. First port of call will be to inspect the thing for obvious shorts or issues, replace power cord with a 3 wire and fuse, and replace electrolytic caps, then insert a guitar signal before the preamp valve grid, and see what happens. Kind regards, Ben |
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Post by Richard on Sept 14, 2021 9:37:05 GMT 12
I really don't think the bell colt will make a suitable guitar amp, not enough gain in the preamp and the speaker is way too small. I think you're better off restoring the colt, as it appears to be in good cosmetic condition and finding something more suitable, like a valve P.A amp to modify.
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Post by harryorgans on Sept 14, 2021 11:39:14 GMT 12
Thanks for the input Richard, I may well go that way. I'm certainly not expecting the colt to turn in to some monster professional guitar amp, and I have proper ones anyway.
I'm more interested to see if it can be an interesting sounding small practice amp
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Post by Philconut on Sept 15, 2021 9:34:51 GMT 12
I suspect that the first twang of a string will send the speaker cone across the room!
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Steve
Society Members
vintageradio.co.nz
Posts: 727
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Post by Steve on Sept 19, 2021 12:00:46 GMT 12
Boo to the nay-sayers, I say  The knobs on your one are hard to find intact (and can be a nightmare to remove), and the dial is not that common... so I'd be tempted as a collector to restore it or leave it as-is - BUT, and its a big but: this is your radio - so you get to decide its fate. If someone else wanted to save it then I assume they had the chance to do so when it was for sale. Bell Colt's were made in the 10's of thousands - maybe 100's of thousands. They are the single-most ubiquitous valve radio in New Zealand by a long margin. Converting one, even one with one of the uncommon dial types, should upset no-one. Don't go drilling holes in the case though - because cases are an ever-diminishing resource - at least until someone stumbles across the dies sitting in the back corner of an old factory somewhere to make new ones (man, that would be an awesome find). Personally I think it'll make an ok practice amp although the Rola speaker in it is likely to have a loose cone - because they are freestanding in the cabinet and not screwed to a baffle, the glue fails over the years and they rattle badly - so you might want to carefully lift the cone around the rim, reglue it and hold it together with clothespegs until the glue sets. Try feeding the guitar in to the wiper (centre pin) of the volume control, tune it off-station, and see what happens - start with the volume right down on the guitar and radio, then slowly bring them up and go from there - it might need a bit of attenuation and tone shaping to get it right, but it should be ok. Keep us posted! Cheers, Steve |
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Post by harryorgans on Sept 19, 2021 21:19:03 GMT 12
Thanks for your input Steve. I'm also thinking it should make a decent practice amp - the valve set of EBC81, EL84, EZ80 is very similar to the Vox AC4 and if the transformers are good it should have potential. The outside is close to perfect, so don't worry - I won't modify it in any way. Inside is quite rough, transformers, antennas, are all loose on their mountings, caps are all waxy and unfortunately the speaker has a tear and looks rough. Two knobs are intact, third one broken but I have superglued the shaft on, will hopefully be OK. I haven't done anything more that inspect the thing so far as I want to tread carefully so when I had some time this week I built this:  DIY Current Limiter made from Mitre10 bits, now has a 100watt bulb installed and I'll plug the radio in tomorrow and see what happens. Ben |
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Post by harryorgans on Sept 20, 2021 14:58:06 GMT 12
Quick update - RF section on the radio doesn't work at all, V1 is broken and everything is a mess. AF section fired up fine. Tone of the amplifier is rather pleasant, but volume is very low. Next step is to check voltages, caps and resistor values
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Post by Radiotech on Sept 24, 2021 23:52:47 GMT 12
I saw that Colt on TradeMe along with a couple of others that were closing about the same time, and I had considered buying it but I have too many projects as it is.
I agree with what's been said already - it wouldn't make a very good guitar amp, not even a practice amp.
Keep it as a nice tidy example of what we produced here last century, make it go and enjoy some good old AM tones.
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Post by Kempy on Oct 16, 2021 8:39:53 GMT 12
You could always repair the radio and build a small AM transmitter, then keep purchasing Bell Colts until you have enough to build the first ever “Wall of Bell Colts”’ similar to The Who ,only with a much lower output and a lot more hum and crackle.
It would certainly work for the intro of “Wish you were here”
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