Hacker RP25A DOA

[logicaluk]

Hi, this is my first post and I had hoped it would have a better start than this, but here goes.

I have just bought a Hacker Sovereign II RP25A off. Chassis number 52874 with a Celestion speaker.

Someone's been in here before, A replacement VHF aerial has been bodged in but the switched, fused, kettle lead mains input is a nice touch, what they fitted is missing, so perfect for the project I have in mind.

My plan is to build a Lithium-ion battery pack and add Bluetooth capability.

But unfortunately, something bad has happened to it. I built the 18V battery pack using 5 18650 cells from an old laptop battery pack and a £7 battery management system. Connecting up the power pack nothing happened, well almost nothing, there was a slight click when the power was applied, but no static. No function from the buttons ether, having read up on this fine forum next step is to clean the contacts on the gram input and phones sockets, but when I took the chassis out of the case I found a nasty stain on the case and two tracks blown off the switch board, the track running from k(red power wire) to the VHF switch and from the VHF switch to C11. I shall replace the missing tracks with some wire tomorrow. I just hope the switch contacts will have survived, could this have been caused by the bodged aerial installation as it appears to have been shorted to the chassis?

[logicaluk]

Turns out, the slight click when power is applied is also present whether the power switch is on or off.
Dan

[murphyv310]

Did you test the radio prior to fitting the lithium ion modification?
5x18650 batteries fully charged are 21v which is a little too high IMHO.

A small bit of advice. Read the forum rules carefully and do your best to follow them, we all trip up occasionally and often without thinking but please take heed of my advice and from the moderating team.

Welcome by the way and enjoy the forum.

[Boulevardier]

If someone has fitted a mains input connector of that sort, then God knows what else they did after fitting it! Perhaps they were a complete "know-nothing" and tried feeding mains direct to the set... If so, they will have done substantial damage. The set will need comprehensive examination to establish what happened and the extent of any damage.

[murphyv310]

It would be useful if you can tell us to where and what the mains lead was connected to?

[logicaluk]

I would like to apologise to the moderating team for not properly reading and understanding your posting rules.

Originally Posted by murphyv310

Did you test the radio prior to fitting the lithium ion modification?
5x18650 batteries fully charged are 21v which is a little too high IMHO.

A small bit of advice. Read the forum rules carefully and do your best to follow them, we all trip up occasionally and often without thinking but please take heed of my advice and from the moderating team.

Welcome by the way and enjoy the forum.

Hi Murphy, the battery pack has a battery management system that brings the voltage down to 18.6V. I didn't test it as I don't have a 18v power supply.

Originally Posted by Boulevardier

If someone has fitted a mains input connector of that sort, then God knows what else they did after fitting it! Perhaps they were a complete "know-nothing" and tried feeding mains direct to the set... If so, they will have done substantial damage. The set will need comprehensive examination to establish what happened and the extent of any damage.

It doesn't look like it's had 240v across it, but who knows

Originally Posted by murphyv310

It would be useful if you can tell us to where and what the mains lead was connected to?

The mains connector wires were cut off, as were the battery connectors

Hopefully the pics attached are of the radio and the damage I found.

[Radiocruncher]

This doesn’t sound good. I suspect that the power supply previously fitted has delivered too much current when a fault has occurred and burnt out the tracks to the switch bank as the current passes through the FM switch. This may have taken out transistors in the amplifier and possibly the IF circuits depending what position the switch was in when it happened. Could be an expensive job considering the price of some of the transistors but well worth fixing as they are great sounding sets.

Have you stripped out the jack sockets and cleaned them manually? Just putting switch cleaner in them rarely clears an open circuit socket. They can easily be bypassed for testing. I’ve restored 2 of these very recently so have included images of the sockets taken apart.

Good luck

Graham

[logicaluk]

Thank you Graham, I shall remove the sockets for cleaning, a few mins in the sonic bath should do the trick. As you have done two recently, are there any caps in there that should be changed as a matter of course (like the waxies in a valve set?)

I haven't looked at replacing the transistors yet, I will evaluate after I have fixed the blown tracks. As I am also going to need a replacement VHF aerial, it may be cheaper to use this one for parts and buy another.
Dan

[murphyv310]

Hi.
The amount of charring on the PCB suggests to me that it's been fed with more than 18v and with substantial current available.
As has been said it could be a tricky repair with many transistors blown.
What a pity as the radio itself looks in nice order.

[logicaluk]

Well it looks like it's toast, I've replaced the blown out tracks, by following the marks left on the board and nothing changed, to be honest I feel a bit of a fool, I should have checked the switch first, I assumed it was OK, but as we all know that makes an ass out of u and me.

I think this repair is now beyond my abilities. I'll have to bite the bullet and buy another.

[logicaluk]

I've just done a deal on a RP25B. Its untested,missing parts and damaged, luckily I have some spares.
Fingers crossed.
I'll start a new thread for it when it arrives.
Dan

[Nickthedentist]

Completely vapourised tracks... that almost looks like it's had 240V mains shoved directly up it!

[Hybrid tellies]

I agree with Nickthedentist. A definite case of someone not knowing what they were doing and connecting the mains power directly to the radio. I have seen this done with other low voltage equipment and the results are always the same.
It will be a very interesting challenge for someone to try and rebuild this radio.

[Nickthedentist]

It may not be a write off, but I'd imagine all the semiconductors would need replacing.

The wound components may well have survived, with luck.

[Mr 1936]

Hi logicaluk, and welcome to the world of vintage radio.

I'm sorry you have got off to a shaky start. I agree with the other posters, it takes a LOT of energy to destroy a PCB track quite so comprehensively. It does seem likely that some IPO ** has connected the AC mains straight to the PCB

** Idiotic Previous Owner. Found in all sorts of fields !

Take consolation in the fact that your dead radio will be a good source of spares, things like cabinet parts, knobs and loudspeakers can be much harder to find than replacement transistors.

I recommend that you buy a bench DC variable voltage power supply for initial testing, which will allow both voltage and a current limit to be set. These supplies are far cheaper in real terms than they used to be.

Good Luck.

[logicaluk]

Thanks I'm just awaiting the arrival of the B, when that's working I'll offer this one up for someone looking for a challenge

A bench power supply has been on my eBay watch list for some time, In fact I missed out on some Thurlby ones just recently. But ill keep looking.
When I get my electronics workshop finished, ill have a bench to put it on, along with my huge military power supply that's been sat in the shed since I inherited it from my grandad. That's going to need a few very large caps' I'd guess.
Dan