EMRFD Message Archive 6273

Message Date From Subject
6273 2011-05-11 12:15:15 Paul old Tripplet 2432 sig gen
I picked up an old Triplett 2432 signal generator for cheap at an auction.

I was really surprised at how well built the thing is. It has separate copper plated boxes around the oscillator, attenuator and band-switch coils.

I handles 75 kHz to 50Mhz in 5 bands.

The band switch has 5 separte sets of coils/trimmers arranged in a rotating barrel connected to a knob on the front panel. Very solid feel to it.

radiomuseum.org shows it as being produced starting in 1946.

I'm trying to decide if I should just replace the two electrolytic power supply caps (and maybe replace the old amphenol mic plug output jack with a BNC) and use it as is.

Or should I re-build a solid state signal generator using the existing tank cicruitry and attenuator. Perhaps try to adapt the EMRFD chapter 7 signal source.

The thing has a build in fixed-frequency audio modulator that I would probably drop if rebuilding.

As is, it uses a 6JS7 pentode as the oscillator and has no buffer stage. Is the lack of buffer state a serious issue? I've never used any tube gear, so I don't have a frame of reference. I'd certainly wouldn't want a solid-state oscillator for a signal generator without a buffer (probably 2 stages).

schematic: http://pacifictv.ca/schematics/triplett2432.jpg

Any thoughts? I know if I asked at on a vintage equipment group that I'd get the answer to fix it and use it. But it was cheap and I have no "moral" or nostalgia issues with rebuilding it.

Paul - K0EET
6274 2011-05-11 13:53:56 Thomas S. Knutsen Re: old Tripplet 2432 sig gen
It's an nice, well build generator. I'd keep it the way it is, just changing
the electrolytics and adding an external variable attenuator. There is a
couple of designs on the EMRFD CD.

When the tubes become unobtainium I would consider changing them to
transistors or FET's.

Just take an good look at the blocking capacitors, they may fail, and that
may not be pretty.

73 de Thomas.

2011/5/11 Paul <paul.d.rose@gmail.com>

>
>
> I picked up an old Triplett 2432 signal generator for cheap at an auction.
>
> I was really surprised at how well built the thing is. It has separate
> copper plated boxes around the oscillator, attenuator and band-switch coils.
>
> I handles 75 kHz to 50Mhz in 5 bands.
>
> The band switch has 5 separte sets of coils/trimmers arranged in a rotating
> barrel connected to a knob on the front panel. Very solid feel to it.
>
> radiomuseum.org shows it as being produced starting in 1946.
>
> I'm trying to decide if I should just replace the two electrolytic power
> supply caps (and maybe replace the old amphenol mic plug output jack with a
> BNC) and use it as is.
>
> Or should I re-build a solid state signal generator using the existing tank
> cicruitry and attenuator. Perhaps try to adapt the EMRFD chapter 7 signal
> source.
>
> The thing has a build in fixed-frequency audio modulator that I would
> probably drop if rebuilding.
>
> As is, it uses a 6JS7 pentode as the oscillator and has no buffer stage. Is
> the lack of buffer state a serious issue? I've never used any tube gear, so
> I don't have a frame of reference. I'd certainly wouldn't want a solid-state
> oscillator for a signal generator without a buffer (probably 2 stages).
>
> schematic: http://pacifictv.ca/schematics/triplett2432.jpg
>
> Any thoughts? I know if I asked at on a vintage equipment group that I'd
> get the answer to fix it and use it. But it was cheap and I have no "moral"
> or nostalgia issues with rebuilding it.
>
> Paul - K0EET
>
>
>



--

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[Non-text portions of this message have been removed]
6276 2011-05-11 16:35:39 KK7B Re: old Tripplet 2432 sig gen
My recommendation is that if you need a signal generator and it works, then use it and don't worry about whether the active device is a valve, tube, discrete transistor, 40673, strange IC, or whiz-bang frequency synthesizer chip that was available from 2003 to 2005. I have both vacuum tube and solid state test equipment in my home lab, and my older well-built tube test equipment is more reliable than my newer solid state instruments with plastic parts. Some of the modern gear is more convenient. Solid state signal generators are easier to kill, in my experience, and the dead part is sometimes a special purpose IC that is no longer available.

If you want a project, then digging into a piece of well-built vacuum tube gear and figuring out how to replace the tubes with discrete transistors can be interesting and satisfying. I tend to reserve that exercise for old gear that I want to take portable and run
6277 2011-05-11 16:52:01 Paul Re: old Tripplet 2432 sig gen
Thanks for the tip! That would indeed not be pretty.

There is a 15pf from the plate of the 6SJ7 into the attenuator that I'll replace just to be safe.

The .1uF from the attenuator to the output jack shown
6278 2011-05-11 17:20:50 Paul Re: old Tripplet 2432 sig gen
Thanks Rick.

I'll certainly put it in working order first.

I've already built the EMRFD Ch7 signal source, which works, but mine is drifty and microphonic (probably due to the cheap polyvaricons I used). Seeing the solid constructi
6279 2011-05-12 10:56:21 scriabini Re: old Tripplet 2432 sig gen
It appears that the buffer is an integral
part of the 6SJ7 pentode circuit - the
plate is pretty well isolated from the
oscillator "triode" consisting of the
cathode, control grid and screen grid.

This was comm
6281 2011-05-12 20:19:16 Bill Wright Re: old Tripplet 2432 sig gen
I would keep the Tripplet as is with appropriate capacitor/resistor upgrades. I
have a Heathkit and
a Eico tracker that are bullet proof.  The twinge to upgrade with modern ic's is
problematic.  An external
stabilized source can be used for sync. even GPS can be applied as a sync
source.
73 Bill
kd5yyk




________________________________
6323 2011-05-18 04:16:01 Tim BandTech.com Re: old Tripplet 2432 sig gen
6324 2011-05-18 06:42:49 Bob Re: old Tripplet 2432 sig gen
Hi Tim et al -

You might check out post 3761. This generator uses "both windings grounded" so it may fit your basic design needs - assuming your band switch switches both windings. This gen has a VERY clean, level output band to band and over any band.

Cordially,
Bob, K3NHI



6328 2011-05-18 11:56:39 Paul Re: old Tripplet 2432 sig gen
Thanks Bob.

I've bookmarked this for future reference.

Paul - K0EET
6332 2011-05-19 07:23:09 Tim BandTech.com Re: old Tripplet 2432 sig gen
6334 2011-05-19 08:33:46 Bob Re: old Tripplet 2432 sig gen
Hello Again, Tim, et al -

Oooops - I should have made better reference in the posting. Please go to the FILES section and look for "50 MHz RF Generator". It's the third item from the top in FILES. Then open this folder and look at the several detailed items therein - I think these will answer a lot for you.

As for measuring harmonic content - frankly I'm not sure there is an easy way around using a spectrum analyzer. In that regard, my HB SA is a somewhat personalized version of the popular QST article, Aug 1998. This is kitted by Kanga US and in fact an upgraded kit is being announced right now at Dayton - as I understand it.

As for how bad a sine wave needs to be to be seen on a scope - boy! - that's a subjective one for sure! In my own case, I feel I can can "see" harmonics around 20 dB down (not so good) on a displayed "sin"e wave. This assumes one is using a scope having several times the bandwidth of the signal being observed. Subjective it is!

If I can be of further assist, please feel free to PM me at kopskib@gmail.com -- I'm curious how your Eico conversi
6335 2011-05-19 08:55:16 Thomas S. Knutsen Re: old Tripplet 2432 sig gen
An simple spectrum analyzer could consist of an balanced mixer, an clean
signalgenerator, an filter and an log amplifier like the one with ad-8307.
That's in basic how the early HP300A Wave analyzer works.

73 de Thomas.

2011/5/19 Bob <kopskirl@cavtel.net>

>
>
> Hello Again, Tim, et al -
>
> Oooops - I should have made better reference in the posting. Please go to
> the FILES section and look for "50 MHz RF Generator". It's the third item
> from the top in FILES. Then open this folder and look at the several
> detailed items therein - I think these will answer a lot for you.
>
> As for measuring harmonic content - frankly I'm not sure there is an easy
> way around using a spectrum analyzer. In that regard, my HB SA is a somewhat
> personalized version of the popular QST article, Aug 1998. This is kitted by
> Kanga US and in fact an upgraded kit is being announced right now at Dayton
> - as I understand it.
>
> As for how bad a sine wave needs to be to be seen on a scope - boy! -
> that's a subjective one for sure! In my own case, I feel I can can "see"
> harmonics around 20 dB down (not so good) on a displayed "sin"e wave. This
> assumes one is using a scope having several times the bandwidth of the
> signal being observed. Subjective it is!
>
> If I can be of further assist, please feel free to PM me at
> kopskib@gmail.com -- I'm curious how your Eico conversi
6336 2011-05-19 11:38:34 Tim Re: old Tripplet 2432 sig gen
6340 2011-05-19 23:03:35 John Kolb Re: old Tripplet 2432 sig gen
Once upon a time, Boonton Electronics made a RF Distortion Meter
(Model 85). Very uncommon - I've never seen
or heard of it other than the one we had at Wavetek in
1967. Basically it's the circuitry of their RF voltmeter,
along with an RF bridge with a series tuned LC circuit in one arm to
notch out the fundamental freq. Two
measurements are made, with the LC circuit open circuit and the
signal remaining with the LC circuit tuned
to resonance. The total hormonic level is the difference between the
two readings.

A similar measurement could be done using EMRFD figure 7.66 with a
high Q series LC circuit used
to notch out the fundamental freq. The ultimate notch depth in this
case is limited by the LC circuit "Q",
while Boonton says the RF bridge "completely" suppresses the fundimental.

John

At 07:23 AM 5/19/2011, you wrote:

>Is there any means of measuring harmonic distortion without a
>spectrum analyzer? By inspecting an oscilloscope trace we should be
>able to state some coarse level of harmonic behavior right? I've
>never actually seen this quantified. Those of us who cannot afford a
>spectrum analyzer have to make do. How bad can a sinewave be and
>still look good on a scope? Sorry I'm a bit OT.
>
> - Tim, AB1AH
6344 2011-05-20 05:52:36 Paul Re: old Tripplet 2432 sig gen
Print a clean sine wave (along with an X and Y axis for alignment), onto transparent material from a computer with a laser or inkjet printer, and use it as an overlay
6346 2011-05-20 10:38:21 Tim BandTech.com Re: old Tripplet 2432 sig gen