"patrick-turner" wrote in message
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[...]
I'm soldering on in retirement and working as I please on gear that is
inherently intersting. I'm currently working on an old wien bridge
oscillator, BWD model 141. It used 4 discrete bjts to get 1Hz to 1Mhz, not
bad, but the square wave was bad, and so I gutted it and am using my own
discrete bjts circuit and 12 switched F per decade - much better than the
old dual gang 15k wire wound Compton potentiometer
which seemed worn and unmatched and which gave F which didn't correspond to
the dial calibrations - typical old junk. Range switches are good, but PSU
and all else needed total remake. I did a similar job to a later BWD 160
which has a function generator chip in it. But output Vo was a very 0.5Vac,
and I put in an amp to lift it, and revised output attenuator, and it now is
a very nice bit of gear.
[...]
"I'm soldering on in retirement...", same for me and I'm happy to say
farewell to the SMD tip and reinstall the old 1/4" nail.
I build a wien bridge osc. in the flower power era, today I find those dual
gang wire wound pots are reliable as the osc. is still working. For the
frequency pot Colvern's are used, not Compton's, but I doubt if that makes a
difference.
Getting the BDW141 sine/square converter back to work properly can't be too
difficult. THD specs for the BWD141 look allright (-60dB), so I wonder why
you gutted it if not for a defective dual gang Compton.
Did you find the documentation for the BDW141?
http://goughlui.com/?p=1343bbbbbbb
http://www.kevinchant.com/uploads/7/..._wave_gen..pdf
Unlike the BDW my DIY osc. has a linear dual gang pot which results in an
"unusual" frequency dial, years later a (salvaged) frequency counter module
was added, based on an ICM7216(D), so I could scrap the DIY
paper-on-aluminium f-dial.
For general tests I use a HP3325A nowadays wich has surprising low THD for a
function generator (-65dB singular H), but for distortion testing the wish
for a (very) low THD osc. remains.
An old Elektor publication describes a wien bridge osc. with 2H at -85dB and
3H at -80dB, but before I start building I'm curious what kind of figures
you obtain with your circuit(s)?
Regards,
Gio Re