Hacker Mayflower RV20 won't work above 96 Mc/s - UK Vintage Radio Repair and Restoration Discussion Forum

Goldieoldie · 1st Dec 2018, 6:57 pm

Hi
I have recapped etc and the radio works well below 96 megs.
Above this there is no reception incl from a sig gen.
I have changed the ECC85 for a known good one. Still the same.
I have changed the grid resistor (220k) as the original had gone high. Same result.
It's difficult to check if the osc stops as its all encased in metal box.
Has anyone had this problem please?
Cheers
Pete

Silicon · 1st Dec 2018, 11:27 pm

What is the main HT voltage and the RF tuner HT voltage?

Have you replaced the selenium rectifier?

Graham G3ZVT · 2nd Dec 2018, 1:47 am

The oscillator is very likely stopping. A non-invasive way to confirm that is to use a second
VHF/FM radio that tunes up to 108MHz and hold the aerial close to the hacker, then follow the oscillator up the band, 10.7 MHz higher and see if, and where it stops.

Goldieoldie · 2nd Dec 2018, 9:24 pm

Yes I did change the bridge to silicon with 120 ohm in series
HT on the output screen is 275 v as per manual
The volts on the tuner were about the quoted manual volts
However the series resistors ( 2 X 6.8k and 22k ) were all a bit high
Replaced all of these and volts now 148 v on the rf side and 111 v on the oscillator
The good news it now works !
I've repaired these Mayflowers before without these issues .Seems this one was a bit fussy
on low volts !
Thanks for your help everyone

Nickthedentist · 3rd Dec 2018, 10:17 am

Well done!

I find the Rs are often way out in these (doubled in value in some places in some examples) but it's knowing which ones it's worth changing that's the clever bit!

The first one I did - about 15 years ago, before I found this wonderful forum - had very poor sensitivity and was very quiet, so I systematically changed all the Rs that were more than about 25% high. The transformation was amazing.

N.

stevehertz · 3rd Dec 2018, 10:25 am

When I 'went through' my RV20 I measured every resistor and changed any that were more than 20% out of designated value. Yes I realise that the original Rs were probably only 20% tolerance to start off with, but that's what I did. And I changed quite a few resistors that were well out of tolerance.

1st Dec 2018, 6:57 pm	#1
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Hacker Mayflower RV20 won't work above 96 Mc/s Hi I have recapped etc and the radio works well below 96 megs. Above this there is no reception incl from a sig gen. I have changed the ECC85 for a known good one. Still the same. I have changed the grid resistor (220k) as the original had gone high. Same result. It's difficult to check if the osc stops as its all encased in metal box. Has anyone had this problem please? Cheers Pete

1st Dec 2018, 11:27 pm	#2
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,162	Re: Hacker mayflower rv20 won't work above 96 m/cs What is the main HT voltage and the RF tuner HT voltage? Have you replaced the selenium rectifier?

2nd Dec 2018, 1:47 am	#3
Graham G3ZVT Dekatron Join Date: May 2010 Location: Greater Manchester, UK. Posts: 18,710	Re: Hacker Mayflower RV20 won't work above 96 Mc/s The oscillator is very likely stopping. A non-invasive way to confirm that is to use a second VHF/FM radio that tunes up to 108MHz and hold the aerial close to the hacker, then follow the oscillator up the band, 10.7 MHz higher and see if, and where it stops. __________________ -- Graham. G3ZVT

2nd Dec 2018, 9:24 pm	#4
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Re: Hacker Mayflower RV20 won't work above 96 Mc/s Yes I did change the bridge to silicon with 120 ohm in series HT on the output screen is 275 v as per manual The volts on the tuner were about the quoted manual volts However the series resistors ( 2 X 6.8k and 22k ) were all a bit high Replaced all of these and volts now 148 v on the rf side and 111 v on the oscillator The good news it now works ! I've repaired these Mayflowers before without these issues .Seems this one was a bit fussy on low volts ! Thanks for your help everyone

3rd Dec 2018, 10:17 am	#5
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	Re: Hacker Mayflower RV20 won't work above 96 Mc/s Well done! I find the Rs are often way out in these (doubled in value in some places in some examples) but it's knowing which ones it's worth changing that's the clever bit! The first one I did - about 15 years ago, before I found this wonderful forum - had very poor sensitivity and was very quiet, so I systematically changed all the Rs that were more than about 25% high. The transformation was amazing. N.

3rd Dec 2018, 10:25 am	#6
stevehertz Dekatron Join Date: Sep 2011 Location: Rugeley, Staffordshire, UK. Posts: 8,827	Re: Hacker Mayflower RV20 won't work above 96 Mc/s When I 'went through' my RV20 I measured every resistor and changed any that were more than 20% out of designated value. Yes I realise that the original Rs were probably only 20% tolerance to start off with, but that's what I did. And I changed quite a few resistors that were well out of tolerance. __________________ A digital radio is the latest thing, but a vintage wireless is forever..