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Forum Free Registration Closed
Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
MRG radiogram is eighty years old.
A 10" PM loudspeaker will replace the missing energised unit. It was removed from the RGD 1046 radiogram, a Goodmans Axoim 10 replaces the unknown brand loudspeaker in the RGD. The field coil has been replaced by a conventional smoothing choke. Because there is no space on the chassis it's mounted above the mains transformer, see first attachment. The Brimar 7D5 output valve was found to have a grid to cathode short. A charged capacitor was used to blast the short off.
The 8 + 8 microfarad smoothing capacitor is dated June 50. It was carefully reformed over a long period of time but in use the hum level was rather high, it really needed replacing. Well now it will need replacing, see the third attachment.
Till Eulenspiegel.
Hi Frank, I was working in the front of the shop fixing a beautiful JVC branded LCD TV when I heard a mighty bang. Of course I knew what had happened the smoothing can had exploded, but there's no doubt about it the capacitor went out in style. According to the Mullard data for the IW4-350 HT rectifier valve the reservoir capacitor value should not exceed 12microfarads and I guess it's the same for the Tungsram APV4. Certainly there's a right old mess to clean up.
Till Eulenspiegel.
Well the yellow cap is a good one, how about some brown paper wrapped around it and varnished?
Frank
"Well the yellow cap is a good one, how about some brown paper wrapped around it and varnished?"
I might well have the original paper capacitor somewhere. When it's found or another one like it the hi-viz capacitor can be used to do a restuff job.
The correct frequency changer valve for this chassis is a Mullard FC13C, the B7 base version of the side contact base FC13 or the continental equivalent, the CK1. https://www.radiomuseum.org/tubes/tube_fc13.html
However, I do have an FC13 and it is possible to fit a B7 to this valve. Also, the successor to the CK1/FC13 is the EK2. Both valves are octodes, grids 1 and 2 function as the local oscillator, G3 and G5 are the screen grids and the signals are injected into G4. G6 is the suppressor grid. To use the EK2 a 33ohm resistor is required to drop the excess heater volts.
Another valve that might work in this set as the frequency changer is the Brimar 15D1 or 15D2, both valves have a 13 volt heater but are pentagrid grid valves. No suppressor grid G6. Heater voltage apart the characteristics are similar to the American 6A7 or 6A8G.
Till Eulenspiegel.
Borrowed the Brimar 15D1 pentagrid frequency changer valve from a Kolster-Brandes radio. Well now we know the front end of the receiver works although the alignment is way out.
Till Eulenspiegel.
On Friday an FC13C octode was fitted in lieu of the 15D1 pentagrid frequency changer valve. The medium aerial and oscillator trimmers tweeked up so now the stations can be tuned in on the correct positions on the tuning scale. The receiver is giving a good account of itself, lots of distant MW stations coming in now. I'm waiting for delivery of a Brimar 15D2. Like the 15D1 and FC13C it also has a 13 volt heater except the heater current is 0.15amp which doesn't matter in this set because the valve heaters are wired in parallel. Let's find out which is the better valve. The MRG radio chassis has a bandpass front end, that is two tuned circuits at aerial frequency and the tuned local oscillator. This leads me to think that the receiver has a low IF, but by 1937 most radio receivers used the standard 465Kc/s IF.
Till Eulenspiegel.
"The MRG radio chassis has a bandpass front end, that is two tuned circuits at aerial frequency and the tuned local oscillator. This leads me to think that the receiver has a low IF, but by 1937 most radio receivers used the standard 465Kc/s IF." In fact it is the standard broadcast receiver IF of 465Kc/s. Well it is now after the IF transformers have been peaked up. I've replaced the final IF transformer with one that was removed from an EMI receiver because the original transformer was some horrible thing that just wouldn't peak up properly. Selectivity is now excellent, sensitivity good for this type of set. Ten feet of wire is all that is needed to receive lots of distant stations. Good sound quality, that Brimar 7D5 is doing a good job as the replacement for the Mullard PEN13C, the valve we assume that was the original type fitted by the manufacturer.
Till Eulenspiegel.
Have no information for the Garrard RC120H motor board so an attempt at making one has started by cutting a piece of plywood to the dimensions of the Garrard RC4 which are 16 X 14 inches.
Till Eulenspiegel.
The motor board was cutout today. The Garrard RC120H has been test fitted in the radiogram. Of course it didn't fit first time and various cutouts had to be made to clear the many parts around the outer edges of the mechanics. It's a perfect fit now so the next stage is fit the three suspension springs and screws which locate the deck in it's correct position.
Till Eulenspiegel.
Nice snug fit, looking good now. 😎
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"Nice snug fit, looking good now" Hi Chris, It took all afternoon to cutout the motor board. A Gentleman came into the shop looking for a decent record reproducer for 78rpm records. I suggested the MRG. He likes the idea of having a radiogram that is eighty years old. It shouldn't be long before this old timer is playing records again. And in terms of sound quality I've got to get this one just right, it's prospective new owner is a musician!
Till Eulenspiegel.
No pressure then.
Frank
Posted by: Till EulenspiegelA Gentleman came into the shop looking for a decent record reproducer for 78rpm records. I suggested the MRG. He likes the idea of having a radiogram that is eighty years old.
Perhaps the last remaining, open Radio & TV shop in the N.E. is changing its business model to providing fine restored vintage, home entertainment products. You never know!
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
Hi Chris, a small but useful number of vintage items are coming in for repair which is of course are pleasant change from struggling to fix LCD TVs. This week it's backlight replacement problems. Those LED strips are not as reliable as the CCFLs.
Till Eulenspiegel.
It's about time this job was signed off.
A Tungsram VP13B has been found and fitted, this metalised valve replaces the clear glass Tungsram VP13K.
Realignment of the tuned circuits. Inject 465Kc/s from the signal generator to the top cap of the FC13C mixer-oscillator valve. Peak up the IF transformers. Reconnect the signal generator to the aerial and earth sockets. Ensure the tuning scale pointer is correctly positioned. Switch to medium waveband. Tune to 200 metres, signal generator set to 1500Kc/s and adjust the MW oscillator trimmer for max output followed by the MW bandpass and aerial trimmers 1 and 2. (Both MW aerial trimmers are connected in parallel.) Tune to 500 metres and set the signal generator to 600Kc/s, adjust the MW oscillator padder for max output. Switch receiver to long waves, tune to 1000 metres, set the signal generator to 300Kc/s, adjust LW oscillator trimmer for max output. Then tune the LW bandpass and aerial trimmers for max output. Tune to 2000 metres, set the signal generator to 150Kc/s, adjust the LW padder for max output. Check that BBC R4 comes in at 198Kc/s. 1500 metres on tuning dial is close enough.
Switch to Short Waveband: Tune receiver to 10 metres, inject 30Mhz and adjust the SW oscillator trimmer for max output followed by the SW bandpass trimmer, no aerial trimmer on SW.
The receiver performs well on the Medium Waveband. Low power transmitter Radio Tyneside comes in on 1575Kc/s so I've peaked up the aerial and bandpass trimmers at that frequency. Long Waveband reception is OK. Short Wave reception is nothing special.
Final reassembly of the radiogram will be done by the weekend.
Till Eulenspiegel.
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