UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 19th Mar 2018, 8:05 am   #1
rogerdup
Retired Dormant Member
 
Join Date: Jan 2018
Location: Chamalières, France.
Posts: 167
Default EF184 on LV30

I don't know if this experiment has been made by LV30 owners before. I made a test putting an EF184 in place of the EF80 at the first stage of the RF unit. This seems to work fine but as expected I got too much contrast and some saturation especially noise on the sound. Looking at the fringe circuit, I noticed that PYE make some change in the components close to the video detect. I wonder if that make sense with a EF184 in place. Does anybody did it?
rogerdup is offline  
Old 19th Mar 2018, 9:46 pm   #2
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: EF184 on LV30

Hello Roger,
I would not recommend the use of the frame grid EF184 in place of the EF80. The EF80 should give you all the gain required, if anything, too much requiring attenuation.

The fringe LV30 was supplied with a manufacturers pre amp that fitted on the spare space at the front of the chassis. A EF80 was employed. It also had a vision interference suppressor circuit that was mounted on the chassis framework.

To use the EF184 in the LV30 will require alterations to the cathode bias resistor and being a TRF circuit, may upset the alignment due to excessive stage gain resulting in instability. Hope this answers a few questions.

An excellent restoration. Well done! John.
Heatercathodeshort is offline  
Old 19th Mar 2018, 10:08 pm   #3
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: EF184 on LV30

Hi Roger,
I can try the EF184 in my LV30C. I'm not sure what the differences are between a normal service area LV30 and a fringe receiver. Most likely the vision bandwidth is reduced to 2.5Mhz in order to increase the gain and reduce noise.
Compare the EF80 with EF184, the former has a gm of 6.8ma/V and the latter 15ma/V.
The EF184 was introduced ten years after the LV30.
From the Radiomuseum:
https://www.radiomuseum.org/tubes/tube_ef80.html https://www.radiomuseum.org/tubes/tube_ef184.html

From R-Type.org: http://www.r-type.org/articles/art-161.htm

DFWB.
FERNSEH is offline  
Old 19th Mar 2018, 10:14 pm   #4
rogerdup
Retired Dormant Member
 
Join Date: Jan 2018
Location: Chamalières, France.
Posts: 167
Default Re: EF184 on LV30

Hello John,
You are right in what you described. I have EF184 at hand and was curious to see what happen when in place of the first EF80. This done, I am back with the EF80 which is doing very well.
My next work on the LV30 is to complete the restoration of the main resistor. I discover that the wire of the 33 ohms sections was much 'cooked' and so ready to open, so I decided to rewind the whole chain. I will have to complete the last section tomorrow.
Nice week !
Roger
Attached Thumbnails
Click image for larger version

Name:	main resistor rebuild.jpg
Views:	122
Size:	86.0 KB
ID:	159509  
rogerdup is offline  
Old 19th Mar 2018, 10:18 pm   #5
rogerdup
Retired Dormant Member
 
Join Date: Jan 2018
Location: Chamalières, France.
Posts: 167
Default Re: EF184 on LV30

Hi David,
Your response came when I was just answering John!
The test was not that good because of the gain too big. I am not wiling to make changes that Pye did with the installation of the fringe preamp. anyway. The set is working perfectly as is.
Roger
rogerdup is offline  
Old 19th Mar 2018, 10:18 pm   #6
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: EF184 on LV30

"The fringe LV30 was supplied with a manufacturers pre amp that fitted on the spare space at the front of the chassis."
JohnHKS has reminded me that the principle difference between the standard receiver and a the fringe area version is the addition of a pre-amplifier module.
The standard LV30 has already impressive vision and sound performance so with the additional amplifier stage the fringe area model must have been one of the most sensitive receivers available in 1950.

DFWB.
FERNSEH is offline  
Old 23rd Mar 2018, 10:25 pm   #7
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: EF184 on LV30

Still yet have to try out the EF184 frame grid valve in the LV30. Roger kindly made and sent to me a perforated metal line timebase screening plate to replace the original non perf part.
The new LTB shield will improve ventilation of the line timebase compartment.
The PL38 and PZ30 valves dissipate a lot of heat.

The picture is off-set to the left and no amount of adjustment of the picture shift plates will centre the picture in the mask.
The fault could be caused by a DC component in the line scanning waveform. However, it is more likely the iron core of the scan coil has become magnetised.
I met this fault in a Pye BV30 and the problem was solved by disconnecting the line scanning coils and momentarily passing a high DC current through the windings.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	PyeLV30LTB_1.jpg
Views:	89
Size:	68.8 KB
ID:	159816   Click image for larger version

Name:	PyeLV30LTB_2.jpg
Views:	96
Size:	96.0 KB
ID:	159817  
FERNSEH is offline  
Old 23rd Mar 2018, 10:55 pm   #8
rogerdup
Retired Dormant Member
 
Join Date: Jan 2018
Location: Chamalières, France.
Posts: 167
Default Re: EF184 on LV30

hi David,
The fault may be caused by the C27A 25v electrolytic capacitor which connect the minus to the horizontal deflection coils. Also electrolytic capacitors C25 and C26 may be faulty. On my LV30, I replaced ALL those capacitors among others and you have seen my picture.
The electrolytic capacitors will be the first I will suspect.

Last edited by rogerdup; 23rd Mar 2018 at 10:59 pm. Reason: complement of information
rogerdup is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:32 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.