Cobra 29 LTD

[kaos513]

Was replacing the caps I found a strange blue cap marked sayno on it c68 says .1uf 25v any ideas what's the right replacement for that cap ? Thanks

 

[NZ8N]

C68 is part of the Mic amp input circuit. .1uF@25v is the correct value.

 

[kaos513]

So is 1uf 25v electrolytic good for it’s replacement ?

 

[d4xycrq]

That diagram posted by NZ8N, above, shows an electrolytic capacitor symbol for C68. You removed a electrolytic.

I'd put a electrolytic back in there. <point> 1 microfarads. .1 Would that circuit be happy with 1 microfarad? You'll be the first to know.

The 29 BOM does mention a Mylar cap. Meh, typo?

73,

Ray

So is 1uf 25v electrolytic good for it’s replacement ?

 

[kaos513]

So far no issues using 1uf 25v

 

[Handy Andy]

For those playing along at home...

C68 is the big Green Chiclet in the middle of the photo.​

@kaos513 - Using a 1uF is "safe" for most - as long as you don't shove too much audio into it while using the radio in a mobile situation - using this in a mobile with a power mike using that values of 1uF can cause some unstable squeal issues from too much audio drive going in.

But again, it's safe for most users. - You also have to remember that the cap prevents the Negative side of the Limiter TR18 - blocks that negative going voltage, from leaking into a filtered and biased audio amp stage - THE CAPACITORS' - if it's polarized, CATHODE (-) End is towards TR18 - else it can fail miserably - there is enough current in the Limiter circuit that it can create an explosive situation if the caps polarity was not installed correctly.

 

[kaos513]

Well the older model of the cobra29 Ltd the c68 symbol is much smaller for a green Maylar cap

 

[kaos513]

For those playing along at home...

View attachment 38451

C68 is the big Green Chiclet in the middle of the photo.​

@kaos513 - Using a 1uF is "safe" for most - as long as you don't shove too much audio into it while using the radio in a mobile situation - using this in a mobile with a power mike using that values of 1uF can cause some unstable squeal issues from too much audio drive going in.

But again, it's safe for most users. - You also have to remember that the cap prevents the Negative side of the Limiter TR18 - blocks that negative going voltage, from leaking into a filtered and biased audio amp stage - THE CAPACITORS' - if it's polarized, CATHODE (-) End is towards TR18 - else it can fail miserably - there is enough current in the Limiter circuit that it can create an explosive situation if the caps polarity was not installed correctly.

Thanks I'm not going to drive this radio like a monster going to be stock

 

[kaos513]

Can I try 0.1 ufcap ?

 

[sunbulls]

I’m curious to know if the original cap you removed has any polarity marks, possibly a black line or a plus mark. A photo would tell more of the story. The small blue cap you described sounds like it could even be a Dipped Tantalum. Regardless, I would still replace it with a .01 and something close to the original type as possible.

 

[NZ8N]

0.1 uF @ 25v is the original value.

 

[kaos513]

Thanks I found one and installed it

 

[kaos513]

I’m curious to know if the original cap you removed has any polarity marks, possibly a black line or a plus mark. A photo would tell more of the story. The small blue cap you described sounds like it could even be a Dipped Tantalum. Regardless, I would still replace it with a .01 and something close to the original type as possible.

It's a cap sanyo

 

[nomadradio]

That one appears to be a non-polar aluminum electrolytic cap.

Only way to get that much storage in a package that small.

73

 

[Handy Andy]

+1 @nomadradio

@kaos513 - Sanyo is not the OEM for the radio.

Someone took care of that radio and tried to upgrade the audio path as much as possible.

You may find more further downstream towards the RX as well as Audio chip routes and path sides.

Since age may be a factor, the areas they tried to upgrade can also add to this problem or create a similar condition later. Look for them and you may want to upgrade their upgrade just to be on the safe side.