Search found 440 matches

by kcbooboo
Sat May 27, 2017 5:23 am
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 6
Views: 278

Re: A real head-scratcher

I concur with your analysis, but why does the grid voltage seem to go further negative (closer to -2100) when the intensity is turned CW, making the trace brighter? I thought noving the grid further negative would cut off the electron flow more, like it does in a triode or tetrode, reducing plate cu...
by kcbooboo
Fri May 19, 2017 3:39 am
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 6
Views: 278

Re: A real head-scratcher

Nothing I can identify. The "P/N" numbers in white ink are Motorola part numbers. Nothing else seems like a number I can relate to.

Bob M.
by kcbooboo
Thu May 18, 2017 4:43 am
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 6
Views: 278

Re: A real head-scratcher

There is a circuit with several "AND" and "OR" gates that does mix a blanking signal with the character generator dot signal. All of that is done at TTL levels and both signals are solid 0-5V levels, nothing inbetween. This modulation signal gets amplified through one stage that controls the maximum...
by kcbooboo
Fri May 12, 2017 2:09 pm
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 6
Views: 278

A real head-scratcher

I'm trying to repair an old Motorola R2001B communications service monitor. It's got a CRT in it that can display text, swept traces, or a mix of both. The text is barely visible while the swept traces are nice and bright. The CRT has deflection plates and works essentially like one does on an ordin...
by kcbooboo
Mon Apr 17, 2017 12:18 pm
Forum: AM Radio
Topic: EO Pulsar 1KW problem
Replies: 9
Views: 668

Re: EO Pulsar 1KW problem

Small tantalum caps (1-33uF) are well-known for intermittently arcing and shorting out, enough to blow fuses or bring power supplies down for the short count. Sometimes they take the resistor in series with the power rail (if the engineer designed the circuit properly) or the foil trace, in lieu the...
by kcbooboo
Sun Apr 16, 2017 6:37 am
Forum: Ham Radio
Topic: IC 706 MkII-G problem
Replies: 4
Views: 147

Re: IC 706 MkII-G problem

The service manual IS available on-line. I took a look at it and it appears they don't use RF brick PAs but discrete FETs. Possibly relays to switch the bands.

Bob M.
by kcbooboo
Wed Mar 22, 2017 5:18 pm
Forum: FM Radio
Topic: High Pitched Tone in FM Audio?
Replies: 23
Views: 1140

Re: High Pitched Tone in FM Audio?

If the holes in the top cover are counter-sunk, then it probably wants phillips flat-head screws. If not, then ordinary phillips round-head or pan-head screws with a split-ring lockwasher and a flat washer. The thread size will need to be determined by trying some other screws of known size, but pos...
by kcbooboo
Sat Mar 11, 2017 2:29 pm
Forum: STL Engineering
Topic: Harris CD Link
Replies: 12
Views: 691

Re: Harris CD Link

I think you're on your own. Harris did the same with their Aurora series of 5.8 MHz link equipment, wanting more than the units cost just to check them out. You should be able to buy another power supply if you can figure out what the original is supposed to be putting out. The size seems to be an i...
by kcbooboo
Sat Mar 11, 2017 2:23 pm
Forum: AM Radio
Topic: INTERNATIONAL CRYSTAL MFG
Replies: 14
Views: 626

Re: INTERNATIONAL CRYSTAL MFG

Considering how crudely the ICM web page looks, I almost get the feeling it's fake and has been spammed. But it is an interesting coincidence that RadioShack's parent company also declared bankruptcy a few days earlier. I too want to get some Crystals for a 10M base station. At one point they were a...
by kcbooboo
Sun Feb 19, 2017 6:57 am
Forum: Radio Studio Engineering
Topic: Quiet UPS
Replies: 12
Views: 486

Re: Quiet UPS

By the way, when I said "extension cord" earlier, I didn't really mean to lay one across the floor and incur the wrath of the fire inspector (been there, done that). I was thinking of running some conduit and making a real branch circuit fed by the UPS, so you can get the constant power from a UPS i...
by kcbooboo
Fri Feb 17, 2017 11:20 am
Forum: AM Radio
Topic: Need Dip Switch settings on (/\/\) Motorola 1310
Replies: 6
Views: 487

Re: Need Dip Switch settings on (/\/\) 1310

Probably the next sequence after 1620 kHz.

Bob M.
by kcbooboo
Fri Feb 17, 2017 4:23 am
Forum: Radio Studio Engineering
Topic: Quiet UPS
Replies: 12
Views: 486

Re: Quiet UPS

I was given an Eaton 5PX-series with what appeared to be battery issues (another one where they waited 6 years before changing batteries) but this one had an odd situation. It worked fine on utility power, running a small electric motor. When I pulled the power plug the front panel said 120V 60.0 Hz...
by kcbooboo
Thu Feb 16, 2017 11:32 am
Forum: Radio Studio Engineering
Topic: Quiet UPS
Replies: 12
Views: 486

Re: Quiet UPS

I too have had the bulging battery syndrome with APC UPSes. I needed to take the top cover off and use a pry bar on an SU2200 that had 8 batteries inside it. In all fairness they were at least 6-8 years old and were far overdue for replacement, and for some reason the whole unit was scrapped - into ...
by kcbooboo
Thu Feb 16, 2017 5:45 am
Forum: Radio Studio Engineering
Topic: Quiet UPS
Replies: 12
Views: 486

Re: Quiet UPS

The APC SmartUPS series, at least the ones I've encountered up to 2200VA, are NOT true on-line units that run the load off the inverter 100% of the time. They pass ordinary AC through via relay contacts then switch to the inverter when utility power fails. The larger units (SU1400 and larger) have f...
by kcbooboo
Tue Jan 10, 2017 7:28 am
Forum: General Computers
Topic: Locked up browsers
Replies: 7
Views: 555

Re: Locked up browsers

When something seems locked up here, I glance over at my router to see if there's any network activity, and there never is. It seems that if an application requests data over the network, it is then suspended until that data is returned, hence the application appears to hang. It has to do with the w...