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Old 26th May 2012, 08:33 AM   #81
M Gregg is offline M Gregg  United Kingdom
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Ahh the ZN414,

Looked like a BC109 made by Ferranti quite sensitive but the selectivity was rubbish.. Just remembered it had a stupid 1.5V supply...try making one of those without any experience...LOL but if I put a diode in I loose .6V... LOL... Took ages to think of an LED with a series diode...though I had discovered the theory of relativity..


I remember building an AM transmitter to pipe cassette music arround the house..my friend who went to work for the BBC had a full home made SW radio rig and an aerial that took us two weeks to get erected. The buzz at the time was to hear Ecuador radio (don't ask I have no idea why, it was a weak station..)

I had a few amps that semed to work as relaxation oscillators...sometimes took weeks to work out why the music sounded great then "tick" thump brrrrrr...power down and music again.. time out seemed to vary with how close your hand was to the circuit....worked well as a theremin.

after trying the move wires arround out came the dreaded books on how to build amps...and a large stock of old 1960's tube magazines donated by various people...help from the school physics department and use of a scope.
RIAA was the in thing for record....perhaps an everthing else thread "memories of early days electronics"..would be good...

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M. Gregg
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Last edited by M Gregg; 26th May 2012 at 08:42 AM.
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Old 26th May 2012, 08:34 AM   #82
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I like the D83 Telequipment...
Oooh, the posh new-fangled one! I'm still using my D66.
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Old 26th May 2012, 05:53 PM   #83
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by M Gregg View Post
Ahh the ZN414,

Looked like a BC109 made by Ferranti .......................perhaps an everthing else thread "memories of early days electronics"..would be good...

Regards
M. Gregg
Happy days for sure... and that's a good idea for a new thread somewhere
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Old 21st June 2012, 10:24 PM   #84
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Hi Mooly!

I purchased a second hand 20Mhz Hitachi scope. Is it good enough to check op-amp stability?

Will this scope show high frequency oscilations working at 20Mhz?

I know a 100Mhz osciloscope is more apropriate but I can't stand it.
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Old 22nd June 2012, 12:46 AM   #85
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I found the answer to my doubt in earlier pages.
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Old 22nd June 2012, 06:07 AM   #86
Mooly is offline Mooly  United Kingdom
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Originally Posted by Audio Maniac View Post
Hi Mooly!

I purchased a second hand 20Mhz Hitachi scope. Is it good enough to check op-amp stability?

Will this scope show high frequency oscilations working at 20Mhz?

I know a 100Mhz osciloscope is more apropriate but I can't stand it.
The Hitachi scopes I have used have been good so get to know it and how it all works

A good 20Mhz "analogue" scope will display frequencies significantly higher than that although with reduced accuracy of course.

Make sure you have some decent probes (a 10-1 type) as these reduce the capacitive loading on the circuit as it is being tested.
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Old 22nd June 2012, 07:18 AM   #87
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The supplied probes aren't the original stock units and look like cheap.

Can you recommend me an inexpensive but realiable probe?
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Old 22nd June 2012, 07:55 AM   #88
Mooly is offline Mooly  United Kingdom
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Something like this which is a switchable 10-1 or 1-1 probe. Good probes can be expensive and it depends on what is available locally.

60mhz Oscilloscope Probe

Any "divider" probe has a small trimmer cap built into it to exactly match the probe to the oscilloscope it is used with. This is adjusted by connecting the probe (when set to divide) to the CAL output on the scope which is normally a 1Khz squarewave. The trimmer is adjusted to give no over or undershoot on the waveform.

Of interest,
How to Build Your Own Oscilloscope Probes
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Old 22nd June 2012, 03:58 PM   #89
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Thanks again Mooly!
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Old 22nd June 2012, 11:50 PM   #90
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You're lucky you got any probes at all... The ones that came with my orig. Hitachi Scope (new!) were nothing to write home about.
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