Search found 448 matches

by kcbooboo
Thu Jul 27, 2017 10:32 am
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 7
Views: 667

Re: A real head-scratcher

There is joy in Mudville today. I purchased a Sencore CR70 CRT tester/rejuvenator for $65 shipped. It looks brand new. Came with all the adapters, including the "universal adapter" (a pod with EZ-clips at the end of five wires) and has the setup book. It passed the field tests. I subsequently bought...
by kcbooboo
Mon Jul 24, 2017 6:47 am
Forum: Everything else
Topic: Mounting stuff to old concrete block wall?
Replies: 18
Views: 899

Re: Mounting stuff to old concrete block wall?

Since I mounted my dryer outlet on wood nailed to the poured concrete wall, here's another funny. When I bought my house in 1987, it came with a washer and dryer (still in service today and working great; the quality went in before the GE nameplate went on). There was a separate circuit run for the ...
by kcbooboo
Tue Jul 18, 2017 5:44 am
Forum: AM Radio
Topic: Antennas for Field Measurement
Replies: 7
Views: 557

Re: Antennas for Field Measurement

I believe Kevin was referring to the previous or original proof-of-performance measurements that had to be done when the station went on the air. Those are your reference, and the signal levels were surely made with an FIM. I have an FIM and a spectrum analyze and Scott loop antenna. There is a cali...
by kcbooboo
Mon Jul 17, 2017 4:34 am
Forum: Everything else
Topic: Mounting stuff to old concrete block wall?
Replies: 18
Views: 899

Re: Mounting stuff to old concrete block wall?

I did a similar thing but to a poured concrete wall. Rather than fight with the drill bit moving around, I used a Hilti nail gun to anchor a piece of 3/4 inch plywood to the wall. I could then mount the dryer outlet to the plywood with ordinary wood screws. Another way that might work is to use your...
by kcbooboo
Wed Jul 05, 2017 1:11 pm
Forum: AM Radio
Topic: Collins 310W-1 Exciter Divider
Replies: 20
Views: 1248

Re: Collins 310W-1 Exciter Divider

Check the MC900/MC800 series on PDF pages 1260-1306: M902, M916, M926, M913, M920 are all RTL flip flops. This logic series accepts VCC=12V. There's probably nothing about the resistors and transistors inside that prevents it from operating with more or less voltage. You could almost build the IC ou...
by kcbooboo
Tue Jul 04, 2017 7:33 am
Forum: AM Radio
Topic: Collins 310W-1 Exciter Divider
Replies: 20
Views: 1248

Re: Collins 310W-1 Exciter Divider

The MC714G wasn't the right chip but it got me into the right section. At least you might find the proper semiconductor family (DTL, RTL, etc) and type of astable multivibrator (i.e. flip-flop) and can fashion something equivalent, even if on a piece of perf-board.

Bob M.
by kcbooboo
Tue Jul 04, 2017 5:03 am
Forum: AM Radio
Topic: Collins 310W-1 Exciter Divider
Replies: 20
Views: 1248

Re: Collins 310W-1 Exciter Divider

Thanks to the exciter PDF, I looked up the Collins part number. That got me to an MC714G. There's a datasheetarchive PDF file of a 1966 Motorola semiconductor book, 22MB. There are LOTS of 8-pin metal (G) flip-flops there, in many different logic families. They have the outputs listed as 1/0 rather ...
by kcbooboo
Fri Jun 30, 2017 5:15 am
Forum: AM Radio
Topic: Collins 310W-1 Exciter Divider
Replies: 20
Views: 1248

Re: Collins 310W-1 Exciter Divider

Could they possibly be "RTL" ICs, round domed epoxy, about 3/8 inch in diameter, made mainly by Fairchild in the late 60s, early 70s? Those preceded "TTL" ICs.

Bob M.
by kcbooboo
Sat May 27, 2017 5:23 am
Forum: Ask the Engineers
Topic: A real head-scratcher
Replies: 7
Views: 667

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: 7
Views: 667

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: 7
Views: 667

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: 7
Views: 667

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: 870

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: 219

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: 1506

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...