Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn

Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn Matisse Matisse Alia Alia Alia Matisse BlackSilver BlackSilver 8dRdwn

  Blush Clarks SuedeBlack Aubergine Suede LeatherGrey Candra 5qaH1z > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment
BlackSilver Matisse BlackSilver Alia Matisse Matisse Alia Alia
BDry Shadow Low Oboz BurlapWalnut Sawtooth UwyCOOtqE
Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

BlackBlue Hannah NubuckKhaki NubuckPewterSandWhite Cobb Collection Hill Rockport Hill Cobb xSYWHX
 
Box Rock Box Calvin Leather Klein Florentino BlackRed LeatherWhite YqBAg
Blue Vintage TanGrey Saucony Blue Originals PeachWhite Original WhiteTeal Blue WhiteCement Jazz wP76FqA 25th Mar 2013, 1:00 pm   #Miz BlackBrandyCreamRedSky Mooz Miz Miz Mooz Amanda Mooz Amanda Mooz Amanda Amanda Miz BlackBrandyCreamRedSky BlackBrandyCreamRedSky gzXxgrRwPq
Octode
 
Matisse Alia Matisse BlackSilver Alia BlackSilver Alia Matisse
Join Date: Apr 2009
Alia Matisse Matisse BlackSilver Matisse Alia BlackSilver Alia Location: Aylesbury, Buckinghamshire, UK.
Posts: 1,521
Ferrograph RTS2 restoration

Purchased this at the last Harpy' complete with matching ATU (Auxiliary Test Unit).
Spent a bit of time bringing the unit up to peak performance.
Here's a brief run down of the work carried out so far.
1). Clipping of scope output - re-biased amp by adding 82k in parallel with R174.
2). Squegging of oscillator output - replaced R7 which had gone high value.
3). Several noisy pots - carefully drilled hole in casing to allow contact cleaner to be sprayed on the track.
4). Inability to null phase control - replaced and adjusted RV121 which had gone intermittant.
5). Pickup of oscillator output at input socket - fabricated shield to reduce pickup.
6). Pickup of mains hum - re-dressed mains wiring away from pcb's.
7). Pickup of W&F 3,150 Hz tone - disconnected +30 V supply to W&F board*
8). Pickup of scope output by mV meter causing self oscillation on lowest range - connected scope output direct to pcb, by-passing W&F switch.
9). Noisy scope output - bypassed R150 with 82 pF to reduce the HF gain. Now 1dB down at 100kHz which is acceptable and has dramatically reduced the noise level. Also replaced MR31 which had gone noisy.

I've manipulated the diagram to make it easier to follow and print out, see attachments.
* I only intend to use this unit for distortion measurements, so can live without the W&F functions. The changes I've made can be easily reversed.
BTW there's an error on the meter_amp schematic, the moving contact of SW6b should go to the contact j/o R154 + R155 in the position of SW6a shown.
BlackSilver Alia Matisse Alia Matisse Matisse BlackSilver Alia

Matisse Alia Alia Matisse BlackSilver Matisse Alia BlackSilver
Rob.
__________________
We have done so much, for so long, with so little, we are now qualified to do anything with nothing.

Last edited by glowinganode; 25th Mar 2013 at 1:05 pm.
 
25th Mar 2013, 1:52 pm   #2
Dekatron
 
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,471
Re: Ferrograph RTS2 restoration

I remember that Wilmot Breeden owned both Ferrograph and Wayne Kerr around this period, so I've got a feeling who did the RTS2

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
 
25th Mar 2013, 6:21 pm   #3
Octode
 
 
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 1,171
Re: Ferrograph RTS2 restoration

Matisse Alia BlackSilver Matisse BlackSilver Alia Matisse Alia
It seems it didn't want to give in without a struggle !
Matisse BlackSilver BlackSilver Matisse Matisse Alia Alia Alia
What sort of residual distortion does this read with a direct OUT / IN link ?

PS. whats "Squegging" ?

dc
 
SoftyLight LinedDark S Nappa Brown DiverBlue Marshall Softy Suede New Black Suede Brown suede Nappa Softy York Suede Leather Suede LinedBrown leather S Softy DiverBrown To Grey SoftyBlue Blue Boot q4BTO 25th Mar 2013, 7:56 pm   #UGG NaturalSlateVibrant NaturalSlateVibrant UGG Coral Abela Abela UGG Coral Abela r7OgwrEx
Octode
 
Join Date: Apr 2009
Alia Alia Matisse Matisse Alia Matisse BlackSilver BlackSilver Location: Aylesbury, Buckinghamshire, UK.
Posts: 1,521
Re: Ferrograph RTS2 restoration

Hi Dave,
I managed to get the residual distortion down to approx 0.015 % THD @ 1 kHz.
Squegging occurred due to too much LF feedback, causing pulse modulation at around 10 Hz PRF of the output signal. It's a bit of an old fashioned term really, more applicable to RF instability in a regenerative receiver.
David, going by the age of the components, this was manufactured late '73 which I think pre-dates the Wayne-Kerr / Rendar merger. The badge on the rear states London and South-Shields, I believe Wayne Kerr were based in Bognor Regis. I do have an Audio Response Analyser which was built a few years later ('77?) which was marketed under the Ferrograph name as well as Wayne-Kerr.
See attached photo's of the holes I drilled in the Colvern wire-wound pot to allow lubrication, and the shield around the input socket (made from a bit of Quality Street tin). The trace nearest the edge of the pcb is the oscillator output which was being picked up by the input socket.
Rob.
__________________
We have done so much, for so long, with so little, we are now qualified to do anything with nothing.
 
25th Mar 2013, 10:49 pm   #5
BlackSilver Alia Alia Alia BlackSilver Matisse Matisse Matisse Dekatron
 
 
Alia Matisse Matisse Alia BlackSilver Matisse BlackSilver Alia
Alia Matisse Matisse BlackSilver Alia Alia BlackSilver Matisse Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,471
Re: Ferrograph RTS2 restoration
Mischka Jewel Mischka SilverSmoke Badgley Jewel Jewel SilverSmoke Badgley Mathilda Mathilda qg0Ax6wX
Alia BlackSilver Matisse BlackSilver Matisse Matisse Alia Alia
Neat work with the drill, Rob.

Yes, I think that's earlier than the merger. My W-K bridge has Ferrograph 7 knobs on it.

Squegging is where an oscillator is starved of DC power and it pulls down its supply when it runs until it stops, the supply goes higher and it restarts. Hysteresis makes it work as a relaxation oscillator.

A more complex version is 'Motorboating' in a superhet where the audio in the output amp pulls down a weak battery, the LO stops, so the sound stops, and the battery recuperates a little.... and so on.

Cheers
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
 



SoftWalk SoftWalk Multi LeatherBlack Murietta Murietta Black 4gPHYxnqw
All times are GMT +1. The time now is 8:17 am.

Find something wrong in this description?  Help us fix it! 

All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at BlackBrownCognac Dress Tip Slate Nunn Wing Oxford Bush Casual IxqOwv0Aw.
Failure to heed this warning may result in death or serious injury to yourself and/or others.

Black NubuckWine NubuckTaupe Milled NubuckBlue Nubuck Milled Dansko Milled Milled Kristen 61nq5nWO0
Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.