Hacker Sovereign 3

[GrahamCo]

A friend asked me to look at his Hacker Sovereign 3 and see if I could get it working (as they do). Completely dead so my immediate thought was the mains power unit. Too easy; power getting to the boards, so the hunt continues. I don't seem to be able to find the schematic anywhere on line. Can anyone post a link to a pdf please?
Thanks.

[Mark Hennessy]

Hi,

You can find the Hacker service manuals at the Hacker Radio Group on groups.io: https://groups.io/g/Hackerradiogroup

Once you've signed up, navigate to the Files section. As well as most of the manuals, there's lots of other useful info there.

You can also search the message archives to find out more about the set.

Hope this helps - at the very least please do let us know how you get on, but feel free to ask for more help - I know these sets a little...

Cheers,

Mark

[Mike Watterson]

Any "lokfit" transistor on the audio amp board is suspect. Often the first stage.
Most small signal plastic TO92 work, if BCE is correctly observed. One theory is that the part was stressed on insertion and an internal wire snaps as failure seems to be specific models of gear. Later auto-insertion manufacturing didn't need the package concept.

[Mark Hennessy]

Anecdotally, I've found the Lockfits to be fairly reliable in these later sets - not perfect, but certainly better than in earlier sets like the Sov2. No idea why, but perhaps Mullard improved their processes?

I'd also be wary of the AC187/188 output transistors (and the bias generator TR3, which is a "T2", which is probably an AC128 or something that didn't meet the voltage spec) - they can suffer from tin whiskers.

But to be honest, the least reliable part of a Sovereign III, including all related sets like the Knights, is the connectors - especially the amplifier connection. They seem to be even worse then the circular 5 pin connectors that causes so many problems with the earlier sets.

And switches and headphone sockets are definitely in the frame. As are the pots (including the power switch on the volume control).

Generally, most faults with these sets are simple things like that. I've needed to do much less component-level diagnosis on these compared to earlier models. Several random faults were caused by oxidisation on component leads (between base metal and plating), but that's not unheard of elsewhere.

[GrahamCo]

Sorry all; I'm getting a bit long in the tooth. I'm a member of the Hacker Radio Group and forgot that RP72 is the Sovereign 3. Got the manual, thanks for putting up with me. (Of course, i may be back when I get in a bit deeper).
I didn't know those audio transistors can suffer from tin whiskers. I have a Roberts radio in the pending pile with dud IF module. So far, I think I've fixed one trial AF117 by cutting off the top, rinsing it out and covering the inside with lead solder.
Thanks All.

[Mike Watterson]

I've replaced AF117s with a Soviet military Germaniums on a Roberts.
On a Bush I found that a silicon PNP 2N3906 worked for mixer-osc and IF amp without any bias change due to emitter resistors and gain, better than the Soviet part.

Bias is tricky on transformerless totem-pole or push-pull audio out, so you usually need all the original flavour parts.