old 'scope for home tube amp work

[Enzo]

Your left side looks different from Tom's left side because your left side is missing the two large knobs.

Also yours is an A, meaning the voltmeter option up top, Tom's lacks that.

[mozz]

You can pick up a used Tenma (mine is labeled Goldstar) or other similar off brand for under $100. There were a bunch that were all the same yet had different names on the outside. Ebay has a bunch, some times the sellers buy out a school or factory and sell them as -is, they usually light up and have a trace but the seller has no idea how to work it.

[Tom Phillips]

...I got this quote from a Tektronix location in Addison, IL, not far from where I am...

That's a great deal! If it wasn't from a Tektronix facility I would be suspicious.

Your left side looks different from Tom's left side because your left side is missing the two large knobs.
Also yours is an A, meaning the voltmeter option up top, Tom's lacks that.

Opps. I see that it was the pic I posted that is missing the knobs. I'll edit the post to replace the picture with a proper one.

[loudthud]

Any Tek scope has proprietary parts. The CRT, the PT, the switches etc. There are usually Tek made ICs in the signal path. If your scope wasn't made in this century, your chances of finding parts anywhere is slim. Many scopes have dual JFETs that weren't Tek made but next to impossible to find. An old scope to cannibalize for parts or ebay are about the only options.

Finding someone to work on the scope is another problem. You can find people selling the service manuals on CD on ebay.

The CRT for the 465 had the biggest production numbers. The T900 series scopes used the same CRT, but you have to change the HV connector. Changing the CRT usually requires complete calibration.

Most scopes with bandwidth over 20MHz have a HV in the range of 25KV. The HV is usually generated by a multiplier in a potted brick. Another proprietary part. Good luck finding one if you need one.

The DMM on a portable scope was an option, not the -A or -B. You won't find a 465A. Those were only released in the Tek factory. I have a 465B that I got for $5. Took about an hour to get it running. I was lucky. Amazed the guys that worked for me!

[Mick Bailey]

Those older Tek scopes are exquisite. Everything in them is (was) the very best quality, but now those parts have not been made for over thirty years. There is IMHO nothing made today that comes even close. They stand up to severe abuse, but stuff does fail. My friend has a Rolls-Royce he runs, plus another 12 for spares. You can pay as much for a pair of headrests as you do for a complete car without the headrests. Tek scopes are the same. Enterprising individuals have bought up every one they can find and are breaking them for spares and this has pushed up prices. Some parts are now almost impossible to find and the kludges to sub in modern components can be convoluted and frustrating.

[mikepukmel]

Thanks everyone, that would explain a *lot*. I started doing searches on other electronics sites, and ebay, was surprised (until reading your posts above) to find many 'not working' units as expensive as the working ones. They're pirating the broken ones for parts, but who knows how many dead ones you'd have to go through to get a particular part. (I'd be sleeping in the garage if my wife came home one day to find the basement filled with broken Tektronix scopes!)

[mikepukmel]

Back to my scope dilemma, Ive seen Rigol, lower end units, for 400-500 range. Its a lot more than I thought Id have to pay for an occasional use used unit to look at waveforms in an amp circuit, but are these a reasonable alternative?

[Enzo]

I needed a scope a few years ago, and decided to try one of the Tenma scopes from MCM. I paid $300 or so. I have been perfectly happy with it. Working on guitar amps is not very demanding in terms of scope needs anyway.

[J M Fahey]

Amazon shows some "top rated" ones, which is good, between $260 and $340 ... not bad at all and I am actually thinking about getting one myself.

And WE do not really need anything above 5 or 10 MHz, fancy triggering and sampling, etc. , we are looking at f*ck*ng analog , band limited *GUITAR* signals on our screens.

I´ve been using a Kikusui "Audio Scope" for over 30 years now, with "just" 1 MHz bandwidth .... way more than I need

And when away from home if pressed I kludge a $5 adapter and look at waveforms with a free computer scope program, on any avilable notebook ....bandwidth 22kHz, (soundcard bandwidth) ... yet it saved my bacon more thn once.

[rjb]

And when away from home if pressed I kludge a $5 adapter and look at waveforms with a free computer scope program, on any avilable notebook ....bandwidth 22kHz, (soundcard bandwidth) ... yet it saved my bacon more thn once.

Details, please?

-rb

[J M Fahey]

Here´s the full thread in TGP:
https://www.thegearpage.net/board/in...-ones.1620645/

The actual attenuator schematics were lost because image hosting site disappeared, I updated the "fancy" adjustable one,

but example pictures refer to the simple one,

which is just a fixed resistive attenuator, 47k in series with 470 ohms which are paralleled with antiparallel 1N4002 diodes to protect soundcard input.
Sharp eyes notice I used a 1k series resistor instead of 47k, that was done because sound source was my phone headphone out, but 47k is correct for signal tracing and troubleshooting on almost any SS amp; the "Fancy" one reaches tube territory.

There is another very high voltage one, NOT USABLE WITH PC SCOPES BUT WITH REAL ONES which allow measuring on Scope killing power tube plates.

[Mick Bailey]

I wouldn't be put off getting an older CRT scope - there are plenty of low-usage examples for not much money. Just make sure it works and that it's cheap enough. There are good brands other than Tektronix that will give you an entirely serviceable scope and not attract the premium price. There are a few checks you can make to give more confidence when you go to buy. For me, if I was buying any scope off Ebay I would assume it has a fault, regardless of what the seller claims.

Do you have any radio clubs in your area, or ham radio contacts? Sometimes those guys have spare equipment that's not actively up for sale, but is well looked-after.

[mikepukmel]

I wouldn't be put off getting an older CRT scope - there are plenty of low-usage examples for not much money. Just make sure it works and that it's cheap enough. There are good brands other than Tektronix that will give you an entirely serviceable scope and not attract the premium price. There are a few checks you can make to give more confidence when you go to buy. For me, if I was buying any scope off Ebay I would assume it has a fault, regardless of what the seller claims.

Do you have any radio clubs in your area, or ham radio contacts? Sometimes those guys have spare equipment that's not actively up for sale, but is well looked-after.

Thanks Mick. This one is for sale on Craigslist (the guy seems to have more than a few for sale) so I can go see it in person, its only about 40 minutes from us, just over the MA/NH border. I will check around for a radio club in Eastern MA, thanks for the tip.

[mozz]

You can also get a USB scope for about $200, there are many others starting at $99.

Instruments

[oc disorder]

I found this a little while ago.
Visual Analyser Project ( current v. 2014 )

Visual Analyzer is a free software oscilloscope made by Sillanum Software.
They describe it as “A complete professional real time software that transforms your PC into a complete set of instruments.
No new hardware is necessary (you can use the Sound Card of your PC).”
News Page

It was written by Alfredo Accattatis who was/is ? a Phd. student collaborating with the University of Rome "Tor Vergata" from 2006 in the "Signal and image Measurements and Processing" group, as Ph.D. student.

About the author

It was originally featured in a now defunct Itallian Electronics magazine who also provided a interface kit for P.C.'s. the LX 1690.



https://web.archive.org/web/20130606...ro-x-pc-1-1690

The wayback machine can find the original articles but they are all in Italian.

The author's website doesn't seem to have been updated since 2014 , but the entire software can be downloaded from there.
It's less than 9 megs.

I recall the original interface required an eprom which doesn't seem to be available.

(works on Win 7 and the Spectrum analyzer works with the inbuilt laptop mics .. well just for fun!)