Hacker Soverign Help Please ! - UK Vintage Radio Repair and Restoration Discussion Forum

AD360 Rob · 19th Dec 2017, 3:51 pm

Afternoon all, I picked up a tidy looking Hacker Sovereign RP18 at the recent auction at Gnosall.
I wasn't expecting it to work and indeed I was not disappointed in that respect. The amplifier seems to be fine barring the odd dry joint (I'll go over it thoroughly at some point but it's working well for now) AM and FM were both dead and the set is filled with AF11x series transistors. AM side, all of them were leaking to the case so I replaced them with Russian GT322Bs, Result, AM now works very well indeed (L.O. transformer quite sensitive to vibration to be addressed later) On to FM and all the AF114s were leaky or dead short to case so these again were replaced with GT322Bs. Now, FM sort of works. weak and distorted signals and possibly some I.F. instability mid band. Experimenting with the AFC/Quiet tuning button revealed that once the button is released when a station is tuned in, the station comes in loud and clear for a second or so then fades back to the distorted weak signals previously. It's as if something is charging up to affect the signal. (C49, the 6.4mfd electrolytic has been removed and tested, found to be less than 0.5mfd away from its value and not leaky) Is it likely that the GT322B isn't a good alternative in FM I.F. applications? I have other transistors I could try including AF200s GT322Vs, AF106s and only 3 AF125s.
Some advice would be much appreciated.

Cheers
Rob

G6Tanuki · 19th Dec 2017, 3:54 pm

I've had similar sorts of things in the past when the big electrolytic capacitor in the discriminator has gone leaky.

[Hint: it's the one whose polarity looks initially wrong!]

AD360 Rob · 19th Dec 2017, 9:31 pm

Hmmm, must admit, I hadn't considered that one, I'll check it out, Thanks.

AD360 Rob · 21st Dec 2017, 9:38 pm

Removed and checked the discriminator electrolytic today, it's fine, capacitance is only slightly higher than printed value and leakage is minimal. I subbed a new one in its place to be sure, no difference at all. I'm virtually certain it's an I.F. instability or gain issue I'll say related to the Russian transistors I've fitted but as it wasn't working at all on FM before I have no point of reference. I might just de-whisker the original AF114s and tack them in to see if that helps. If it does then I'll need to get hold of some AF124s

paulsherwin · 21st Dec 2017, 9:54 pm

It's very unlikely to be a problem with the transistors. Have you checked the voltages in the FM section?

19th Dec 2017, 3:51 pm	#1
AD360 Rob Hexode Join Date: Jun 2012 Location: Chester, Cheshire, UK. Posts: 421	Hacker Soverign Help Please ! Afternoon all, I picked up a tidy looking Hacker Sovereign RP18 at the recent auction at Gnosall. I wasn't expecting it to work and indeed I was not disappointed in that respect. The amplifier seems to be fine barring the odd dry joint (I'll go over it thoroughly at some point but it's working well for now) AM and FM were both dead and the set is filled with AF11x series transistors. AM side, all of them were leaking to the case so I replaced them with Russian GT322Bs, Result, AM now works very well indeed (L.O. transformer quite sensitive to vibration to be addressed later) On to FM and all the AF114s were leaky or dead short to case so these again were replaced with GT322Bs. Now, FM sort of works. weak and distorted signals and possibly some I.F. instability mid band. Experimenting with the AFC/Quiet tuning button revealed that once the button is released when a station is tuned in, the station comes in loud and clear for a second or so then fades back to the distorted weak signals previously. It's as if something is charging up to affect the signal. (C49, the 6.4mfd electrolytic has been removed and tested, found to be less than 0.5mfd away from its value and not leaky) Is it likely that the GT322B isn't a good alternative in FM I.F. applications? I have other transistors I could try including AF200s GT322Vs, AF106s and only 3 AF125s. Some advice would be much appreciated. Cheers Rob

19th Dec 2017, 3:54 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	Re: Hacker Soverign Help Please ! I've had similar sorts of things in the past when the big electrolytic capacitor in the discriminator has gone leaky. [Hint: it's the one whose polarity looks initially wrong!]

19th Dec 2017, 9:31 pm	#3
AD360 Rob Hexode Join Date: Jun 2012 Location: Chester, Cheshire, UK. Posts: 421	Re: Hacker Soverign Help Please ! Hmmm, must admit, I hadn't considered that one, I'll check it out, Thanks.

21st Dec 2017, 9:38 pm	#4
AD360 Rob Hexode Join Date: Jun 2012 Location: Chester, Cheshire, UK. Posts: 421	Re: Hacker Soverign Help Please ! Removed and checked the discriminator electrolytic today, it's fine, capacitance is only slightly higher than printed value and leakage is minimal. I subbed a new one in its place to be sure, no difference at all. I'm virtually certain it's an I.F. instability or gain issue I'll say related to the Russian transistors I've fitted but as it wasn't working at all on FM before I have no point of reference. I might just de-whisker the original AF114s and tack them in to see if that helps. If it does then I'll need to get hold of some AF124s

21st Dec 2017, 9:54 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,939	Re: Hacker Soverign Help Please ! It's very unlikely to be a problem with the transistors. Have you checked the voltages in the FM section?