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Anonymous
| | Posted on Monday, July 02, 2001 - 12:12 am: | 
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Posted on another forum!
Having been a long time "lurker" in a number of CB Radio forums, I've read many opinions about lots of topics, and although frequently I've been tempted to post, I never have, until now. Here's my personal experience regarding this topic, the Turbo Tune radio modification from a mail order/internet company in Longview, Texas.
I ordered a SuperStar 3900HP from the aforementioned company. My order was for the export version, peaked and tuned, and specifically _not_ Turbo Tuned. I wanted a multimode radio with expanded frequencies for my test bench; the SuperStar would provide both a comparison radio and a means of verifying my work on the out of band radios I sometimes fix, but I did not want any modifications.
The radio, when it finally came (it did not arrive in an "express" manner!), was Turbo Tuned. Both the shipping invoice and the box indicated so. (But I wasn't charged for the modification!) I was disappointed, because I wanted a stock radio, but it did provide an opportunity to see for myself exactly how a Turbo Tune would work. Here's what I saw ...
Without opening the radio I put it on the bench, powered it with 13.8vDC, and keyed the transmitter. Carrier power, as measured on my oscilloscope, was 10 watts into a dummy load. Suspicious for a unit with dual 2SC2312 finals. I then whistled into the mike. What a mess! Hard clipping of both positive and negative modulation peaks; it was a very ugly signal, it looked like a square wave! The peak output power at the positive flattops was 43 watts. I experimented with different intensity whistles, and noticed with lower level tones the positive peaks would flattop before the negative peaks saturated. In other words, it appeared that the "NPC" modification was incorrectly done. I was tempted to send it back, but couldn't believe a quality business would ship something so bad. I thought maybe something was damaged in shipping, so decided to look around.
I pulled the covers off the radio and gave a quick visual inspection. No visible damage, but some circuit changes. The AM Mod section of the radio had resistor R238 changed from 5.6K to 27K. The circuitry at the emitter of TR49, the AM Mod Amp, was bypassed with a 390 ohm resistor in series with a 1N4148 diode, cathode to ground. There are also two resistors tacked onto the back of the board, and a few capacitors around the driver and final transistors that may not be original. I buttoned the box back up, and tried a radio check.
Got a good report from a driver on 19 who's own radio was loud and nasty; he liked the way the Turbo Tuned SuperStar "kicked gritty ass". A local friend said it had a harsh tone on AM, and was bleeding +/- 5 channels at about three miles. Sideband didn't sound as bad, but had a bit of a chirp and still didn't sound good. All in all, a disappointing new radio! At least I didn't _pay_ for the Turbo Tune!
I decided not to return it. The radio is sitting on the back of my bench, and maybe in a week or two I'll go through it and figure out all that was done and then restore it to stock condition. It'll be an interesting exercise!
If someone had brought this radio in for me to repair, I would tell them to never go back to the tech who had done such an amateurish hack job. Their advertising is correct; as far as I've noticed, no parts have been removed. That doesn't mean anything, if circuitry is paralled and resistors are raised to a higher value, it can be just the same as cutting out components.
My own opinion, based on my own experience, is the Turbo Tune as sold by that company is worse than bad, it's a rip-off. I recommend avoiding it just based on the lack of sound quality and the splatter. Who knows what the mod will do to reliability?
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The word is getting out, so don't fall into the Turbo Tune trap. You can find them cheap 2nd hand since people are getting out of these while the getting is good, or not so good in my opinion! |
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