Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 06 Feb 2011 10:29:07 -0600
Communications audio isn't full and robust. It has a limited bandwidth by the IF filters and proper audio to limit you hearing atmospheric and circuit noise, hum, and rumble. Adding bandwidth to any
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 06 Feb 2011 20:20:23 -0600
Looking at schematics I don't see anything but the notch filter inherently limiting bandwidth on the IF/AF board. Maybe its that notch filter not getting out of the way when not in use. Maybe its the
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 07 Feb 2011 10:15:43 -0600
Dual, single, triple, or quadruple 220K log pot is not going to be a catalog item. 250K, maybe, but 500K has the best odds at a shop specializing in fixing guitar amps. There are some of those on lin
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 07 Feb 2011 10:29:44 -0600
As far as I can tell, based on down loaded VI and VI+ manuals, there is no VI without a DSP. That the mods making the VI+ were all in firmware in a plugged in EPROM or two on the same hardware board.
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 07 Feb 2011 10:59:59 -0600
Yup, I see that. I just searched Mouser and Digi-Key for dual pots and there weren't many to be had, and none with a quarter inch shaft and 3/8" bushing or 220K like those from Maplin. Those I found
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 07 Feb 2011 23:32:39 -0600
There are many factors in sound equipment, some due to active device nonlinearities, some to clipping characteristics, and some to impedance matching. Solid state circuits tend to swing almost all th
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Mon, 07 Feb 2011 23:35:13 -0600
Cramolin does not recommend DeoxIT for pots. It might dissolve the carbon track, but they do make a product designed for pots. Steve found a pot at Maplin with it looks like the perfect specs to fit,
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Tue, 08 Feb 2011 10:29:11 -0600
Except that the metric shaft bushing is not very long and the shaft is short and it doesn't have PC board pins, the shaft is the right diameter. 73, Jerry, K0CQ You might check out Mouser part number
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Tue, 08 Feb 2011 10:55:45 -0600
That's quite a bit to digest, with a lot of it over my head, but I do see things I agree with and some things I had not realized. I'd like to make sure I get this if you don't mind. There are many fa
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Tue, 08 Feb 2011 13:09:54 -0600
<SNIP> because of the nature of the tube's ability to clip harmonically, whereas a solid state amp will just distort everything evenly to the point where it sounds like mud. Hmm... I suppose that wo
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 09 Feb 2011 11:19:13 -0600
My scheme of shunt loading a linear pot probably isn't a lot better than the log pot, needing to be reverse log. Maybe using a series resistor on the wiper of would band spread the HF end better. Mou
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 09 Feb 2011 17:16:00 -0600
The spray can of Cramolin R5 that I have says "packaged for Caig Labs." I have had decent results but don't like spraying the insulation around a contact with it. So I've been using a dropper bottle
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Wed, 09 Feb 2011 17:19:18 -0600
Many aerosol products changed from Freon 12, a product that didn't cause immediate problems with user contact to propane that also didn't cause contact problems but burns really well to the distress
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 10 Feb 2011 00:50:05 -0600
.pdf is more universal than .doc. And can be set up to be edited, e.g. entries in fields changed or added. Both along with open office document format would be more useful. Not all admit to reading W
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 10 Feb 2011 13:47:04 -0600
The processor chips are available from multiple sources. I did just find that the CODEC that interfaces the DSP to the analog audio is not available. A TLC32041 is its number. I have gone to the TI w
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 10 Feb 2011 17:10:03 -0600
From K1FK about the chips on the OMNI VI control board. He's dug deeper than I have. Some parts the makers do show as obsolete, but I have inquiries to TI and AD about the CODEC. Motorola PLL chips h
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 11 Feb 2011 01:28:55 -0600
Digging out the data sheets from that maker, it shows pots with 1/4" shaft and 3/8" bushing, choice of two bushing lengths. That's on the data sheet offered by Maplin. Digging deeper the factory data
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 12 Feb 2011 10:00:08 -0600
There ought to be 6.5 in and 10 in. There will be 3.5, 6.5, 10, and 16.5 on the chip output. The two mixer products, sum and difference, 3.5 and 16.5 should be about equal strength and if the mixer i
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 12 Feb 2011 13:25:10 -0600
I did get a quote from Omeg. Their part with the closest match would have been 220k with a reverse log taper, the correct size spindle bush, a genuine 1/4" spindle (not 6mm) and the correct length. T
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 12 Feb 2011 14:39:05 -0600
At its age, carbon comp resistors will have drifted. Up in value unless IRC which weren't carbon composition resistors anyway. And the oiled paper capacitors were leaky when new, worse now. And a mic