Transmission1

Hi guys, After a bit of advice if possible?

recently bought a Uniden 2830 and it has at least one problem. I've read a lot of issues can be resolved by changing all the electrolytic capacitors and removing the old glue stuff.

I think it's an early version as it's a bit like the Mk1 Cobra 148 gtl DX. Covered in components on the solder side of the board and weird and strange things generally like diodes in transistor positions and capacitors in diode holes.

I'm trying to change the capacitors like for like rather than use a service manual or "capacitor Kit" as apart from the problem with the readout, it does seem to work... but there are two instances of capacitors linked in series, Negative leg to negative leg, and then the positives stuck through the holes of where a single cap would normally go. Both caps are of the same value in each pair.

I can easily just copy as they are currently, but haven't seen this before so wondered if it was just a bodge, or if there's a reason for it?

Cheers

OH WOW, that will be a mind churner for sure. like you I have never seen caps hooked up this way. maybe some one else has seen this. the only parts hooked this way I have ever seen are diodes. the old Cobra 138 and 139 had some diodes that way and I think some of the 858 PLL president base radios came out with diodes put together that way.
good luck on your search.

Yeah, I think it was from the factory as they had the glue around them, and the radio seems standard without any mods.

I've attached some photos.

I cannot help thinking "Botched Job"
Caps in series are used to reduce capacitance but I would have thought that they should have been coupled +ve to -ve.
Don't electrolytics go bang if coupled up the wrong way?

Both capacitors would act as a non-polarised cap, (with half the rated capacitance) is my guess.

sickboy wrote: ↑28 Apr 2018, 20:35 Both capacitors would act as a non-polarised cap, (with half the rated capacitance) is my guess.

Correct, and half the value if each one is the same.
Common way of doing it, but looks a fudge from a manufacturer.

Thanks guys!

make sure you change all the 10 volt caps to at least 16 volts. the 10 caps are boarder line for the 8 volt rail they are in. this will make them work a lot better in the circuit they are in.

Changing them for 16V caps will have absolutely no effect on the way the rig works, it might help them last longer if you choose good quality parts but you should choose good ones even if you can find 10V ones.

The original 10V been working for 25 years so how much value it adds is debatable, plus, unless the 8V rail is really crappily regulated then there's absolutely no need to increase the working voltage but if you're going to replace them all anyway then it's far easier to get hold of 16V parts than 10V ones so why not.

The back to back caps are a completely valid way of making a non polarised capacitor and has been used in loads of things, they should be +--+ as both ends can go positive in circuit.

Thanks guys.

I'm using good quality and using at least 16v to save having to do it again anytime soon.

Now I know what they were trying to achieve with the back to back caps I've found quite a bit about it online. I've decided to swap them out for non-polarised to make it a bit neater.

Cheers

I've only ever had one of these radios , and I had to change about 4 faulty 10Vs , and a couple of other ones on it . Never seen so many caps go bad in a radio .

Well after changing around a million crappy grey electrolytic capacitors it seems to all be working! The LCD problem and auto squelch problems resolved and the radio is sounding good.....

mutley wrote: ↑05 May 2018, 22:44 Well after changing around a million crappy grey electrolytic capacitors it seems to all be working! The LCD problem and auto squelch problems resolved and the radio is sounding good.....

Good to hear it . I think a recap of these radios is a must .