Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Restoration of 60's Viking RCS-506 tuner/amp for CF Eaton
Restoration of 60's Viking RCS-506 tuner/amp for CF Eaton
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th November 2017, 01:27 PM   #1
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
Default Restoration of 60's Viking RCS-506 tuner/amp for CF Eaton

Hi from PEI,
First post, even though I have been a member for quite a while ...
I am an old retired engineer who last built stereo (valve) amps as a young BBC engineer in the early 60's. We have a CF Eaton stereo console from ca. 1963 with Viking RCS-506, and a Collaro auto change record player..
The cabinet has been restored and revarnished, and the Viking is in good shape. The cabinet has always been indoors, and there is no rust on the chassis, and the face plate is almost unmarked.
AM/FM Tuner mounted on main chassis, and amp has 5U4BG, 7025A and 6BQ5 output tubes in SE mode, but it has not seen power for over 10 years...
I have my light bulb tester ready, but have not applied any power yet. Transformer checks using DVM to look at resistance values show at least the same resistance values on secondaries either side of the center tap in the power transformer.. Long way to go yet...
To cut a long story short, my view is, that restoration means just that... Replace any component which is Kaput, or 'suspicious', recap electrolytics, paper caps. Clean and polish, check resistors, transformers, tubes, check voltages when power can safely be applied.
If I replace chunks of the circuit with a new design, then I feel that am not performing restoration, and I might as well completely gut the chassis, and use it as the home for a completely new amp...
It has all things like grid leak bias in the input stage after the volume control 1M pot. Global Negative feedback,. It designed for ceramic cartridge, so no RIAA circuits, power supply has capacitance input filters (no chokes)..etc...
That is how it was designed and built between 1961 and 1963.. I do need to bring the a.c. input up to snuff, as there is no fuse, unpolarized plug, and safety is a prime concern in this area.
Am I being overly altruistic here... Maybe it is an old man's nostalgia for a simpler unchanged world...lol..I've attached some pics of the cab and chassis.. The AM/FM dial is "real glass", and the power transformer is a serious lump of iron.....The brown stain on the tuner chassis in the second pic top right, is old glue or varnish, not rust.
Any observations on restoration vs modification...
Regards Richard
Attached Images
File Type: jpg DSCN2475.jpg (835.5 KB, 70 views)
File Type: jpg DSCN2476.jpg (662.2 KB, 68 views)
File Type: jpg DSCN2479.jpg (755.8 KB, 67 views)
File Type: jpg DSCN2477.jpg (957.5 KB, 68 views)
  Reply With Quote
Old 8th November 2017, 01:52 PM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
As a fellow retired electronics engineer who built his first 30Watt valve amplifier using EL34 x 2, ECC81 phase splitter, ECC83 driver and pre driver with EF86 RIAA preamp back in 1961.
I would bring the AC up through a bulb limiter, (just in case) and if OK with heaters, power off, insert the rectifier and then monitor the DC across the smoothers when powered up.
These amplifiers were built to last and if no hum, then I would assume things are good and change nothing unless there is a problem.
If it is live chassis design, ensure the power cable is polarised correctly with neutral as chassis. That was the system then and for the likes of us, see no reason to change it unless the chassis is floating and then in that case fit 3 core flex with a BS1363A plug top.
Don't let the older stuff die!
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 8th November 2017, 02:06 PM   #3
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
Thanks John..
I'll let you know what happens.. It is well built, all by hand,(not a pcb in sight)...
It appears to be live chassis, but as yet I have not powered up, because my bulb limiter wasn't ready......
I also remember my first loudspeaker,which was comprised of sand sandwiched between plywood sheets (separated by 2x4 or similar pieces of wood) with a hole in the middle for the speaker. The contraption was angled across 2 walls in a corner, and voila.. infinite baffle !!!
Rgds
Richard
  Reply With Quote
Old 8th November 2017, 02:58 PM   #4
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
If I understand you correctly, you would not firstly replace the electrolytics prior to bringing up rectifier... They look to be in good shape, no rust, etc, and no obvious short circuits to ground, but is it really wise to do this, after all this time with no power on them...(at least 10 years)
My German Shepherds will not be amused if the caps go "bang...."
Rgds
Richard
  Reply With Quote
Old 8th November 2017, 04:25 PM   #5
DF96 is online now DF96  England
diyAudio Member
 
Join Date: May 2007
Unlikely to be live chassis. It has a mains transformer and 5U4 rectifier.

If unused for 10 years or so the PSU electrolytics may need some reforming, but you may get away with letting them do this in operation. I would attach a meter to the reservoir cap and monitor the voltage. If it comes up fairly smoothly when the rectifier cathode heats up then you may be OK. However, I would keep the first 'switch on' fairly short and look out for any funny noises or funny smells. If it can keep some voltage then a second 'switch on' (still with the lamp in circuit) can be a bit longer.

The second thing to check for is leakage in the coupling cap feeding the output grid. Put a meter on the grid and check that the voltage remains near zero. If it rises than you have a leaky cap or a gassy valve. The latter may recover; the former will not.

Having checked these two items there is much less that can go badly wrong, so then you can take your time to find and fix any other faults and then deal with potential future faults.
  Reply With Quote
Old 8th November 2017, 04:30 PM   #6
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Usually, if you power up gently and observe smell, movement and crackles, there should be no issues.
Older electrolytics tend to dry out and go open circuit due to the nature of the manufacturing process. Newer electrolytics, are packed very tightly and heat up quickly if there is a problem.
I am not saying they will all be fine but the chances of a short circuit is quite remote.
As DF96 says, keep a constant eye on them and listen for issues.
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 8th November 2017, 04:39 PM   #7
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
Thanks to both of you for your advice.. Much appreciated.. It has been a long time since I did any real engineering !!!! It is surprising how quickly some things come back, and how other things are lost for ever
As Bertrand Russell once remarked.."No matter how eloquently the dog barks, he cannot tell you that his master is poor, but honest"
Richard
  Reply With Quote
Old 8th November 2017, 06:57 PM   #8
Eli Duttman is offline Eli Duttman  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Definitely replace the electrolytic capacitors. As was previously posted, they literally dry out over time. The modern product is much better in all depts., especially ESR and volumetric efficiency.

If you value your LPs, the Collaro/ceramic cart. combo. needs to go. A cost effective, good sounding, and physically small RIAA phono preamp is Jim Hagerman's Bugle2.
__________________
Eli D.
  Reply With Quote
Old 8th November 2017, 07:21 PM   #9
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
Don't worry, I have a separate stereo system with Linear Tracking turntable, and magnetic cartridge. My vinyl collection dates from early 70's to mid 80's. They have been very carefully looked after over the years., and are stored in Master sleeves inside the album covers. The Collaro turntable will be cleaned, and put back in the cabinet as a show piece, but it basically fills the hole it came out of..
Thanks for the advice.. For young people today who were not brought up in the vinyl age, your observation is very pertinent..
Have a good week, and regards from Atlantic Canada..
Richard
  Reply With Quote
Old 8th November 2017, 07:50 PM   #10
myrddin is offline myrddin
diyAudio Member
 
Join Date: Mar 2016
I ordered replacement electrolytic caps, and replacements for the few paper caps that are in the amp a couple of days ago... I had planned to leave the old cans in place, after cutting their connections, and wiring the new caps in place under the chassis where there is plenty of room. I kept to the original values, but will be easy enough to obtain larger values (except for the input cap) at a later date if I feel it is necessary...
I will replace the caps before any power testing, as it also gives me an opportunity to check the values of the resistors in the CR filters, once I have disconnected the filter electrolytics...
Thanks for your patience folks
Regards
Richard
  Reply With Quote

Reply


Restoration of 60's Viking RCS-506 tuner/amp for CF EatonHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Beware - An online viking! hedu99 Introductions 7 1st June 2017 01:50 AM
First Post, Viking/T Eaton co Tube Amp Issues! *Pictures* Largen Tubes / Valves 20 2nd September 2013 02:04 AM
Fisher Tube Tuner Restoration Walkthrough LinuksGuru Tubes / Valves 7 15th November 2011 02:15 PM
T Eaton Viking schematics? blindbrett Tubes / Valves 3 29th November 2008 12:12 PM
Wanted-Tannoy Eaton-HPD295A crossovers felixx Swap Meet 0 23rd September 2008 11:56 AM


New To Site? Need Help?

All times are GMT. The time now is 01:30 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki