CB Re-caping

[Philomath]

I see I'm in the right place for advice. Thank you all.

I'm interested to know if you guys flush mount the new cap, or leave some leg length sticking up like a factory job? I've always flush mounted cap on my circuit builds.

 

[MKwrench]

I see I'm in the right place for advice. Thank you all.

I'm interested to know if you guys flush mount the new cap, or leave some leg length sticking up like a factory job? I've always flush mounted cap on my circuit builds.

Me too, I hate when they float above the board. Larger ones might even get a drop of adhesive. Gorilla glues Cear Grip Contact Adhesive, It remains removable.
I've heard once that some might need the space between the board, *Inductance*? interference*? Anyone know?

 

[brandon7861]

I would mount them flush whenever possible, especially in a mobile rig. Powered subwoofers (especially the class D ones due to the larger filter components) often have bad solder joints from the parts moving relative to the board. I dread the day my friend brings that miserable Alto back for repair.

The capacitor has mass. If the radio vibrates, the capacitors mass tries to keep it in place, so as the radio vibrates, the leads at the board are constantly flexing and straining the solder joint and pad.

Theres likely so much inductance in the wound foil construction already that the additional inductance you get floating it a mm or two off the board is relatively insignificant to the DC and audio stuff these electrolytics are used for. Ceramics and RF, now that's a different story.

 

[Night Stalker10]

Me too, I hate when they float above the board. Larger ones might even get a drop of adhesive. Gorilla glues Cear Grip Contact Adhesive, It remains removable.
I've heard once that some might need the space between the board, *Inductance*? interference*? Anyone know?

Sometimes you have no choice but to let the capacitor show a little leg (ahem), on the components side. The reason is because the newer caps today, are sometimes smaller in diameter than the caps that the 40 year old PCB were designed for. As was mentioned earlier. When I run across this problem, I just leave the negative lead straight through the hole in the PCB, and then bend the positive lead straight out on top of the board, and bend another 90 degree through the hole. This allows the capacitor to be flat on the board. The best part about doing it this way is it still looks somewhat professional, and it's very handy to test the capacitors voltage for trouble shooting with out flipping the radio over and trying to locate the positive lead on the solder side.

 

[nomadradio]

Capacitor value depends on the circuit. In some, the larger cap makes no difference that you can see or measure. And in some circuits you'll disrupt an intentional time delay.

73

 

[wavrider]

Klondike Mikes cap kits has been my go to for years,,always spot on and with good quality components.
We never mounted any type of discrete component flat on the circuit board unless it was designed to be.
transistors caps, resistors dips, etc etc all were raised above the circuit board.
2M Micro miniature repair Naval aviation. Reason they told us techs was better air flow around the components.

 

[Philomath]

Yeah that's a good point. the other thing that I was thinking is that on a mobile radio the longer legs would help absorb some bumps, like a shock absorber rather than being too rigid and cracking solder joints. My radios will likely never go mobile, so I think I'll go with your recommendation. a couple of mm gap can't hurt.

 

[Philomath]

Klondike Mikes cap kits has been my go to for years,,always spot on and with good quality components.

Yes, Klondike Mikes stocks good quality components, however as I stated earlier, the exchange rate and postage make it cost prohibitive for me. My estimated check out price came to almost $70.00. AUD. Thank you for your input, best regards,
Walt.

 

[Philomath]

I got a bit bored.

 

[Philomath]

Just when you thought the thread was done, I'm sneaking in again.

So I've ordered capacitors from Element14, they have an outlet here in NSW and they were the only ones that had all that I needed. All the caps I ordered are 50v and will fit. I chose Wurth Elektronik for most of the caps and Multicomp Pro for the rest, I spent $74 au for enough caps to do both the Cobra and the Washington with some to spare. I qualified for free post.

So my journey begins.

 

[MKwrench]

I got a bit bored.

A few things I've picked up were to beef up a few of the caps for the regulator and audio chip.
For C172 I'll use a 2200 or 3300uf and C181 gets a 1000uf. These help keep the whole radios voltage steady.
If you leave C232 empty it will eliminate the muting between channels while the channel knob clicks.
Using a 10uf for C174 seems to add a little width and compression to the AM audio.
Or the swing mod at C174 with a 1000uf going directly to the regulator.

 

[loosecannon]

A few things I've picked up were to beef up a few of the caps for the regulator and audio chip.
For C172 I'll use a 2200 or 3300uf and C181 gets a 1000uf. These help keep the whole radios voltage steady.
If you leave C232 empty it will eliminate the muting between channels while the channel knob clicks.
Using a 10uf for C174 seems to add a little width and compression to the AM audio.
Or the swing mod at C174 with a 1000uf going directly to the regulator.

MKwrench,

those are all good changes, but there is a better mod for the audio.

try changing the value of R228 to 1.2K and then adding a 1uf non polarized cap from pin 9 of the audio chip to the junction of R194/R228/D36.

Leave the limiter intact and on the versions that have a fixed value instead of an AMC pot you'll have to change that 10K resistor to a variable pot.

now adjust the AMC using the scope to get the negative peaks just under 100%.

note, this mod only really does anything if you are lowering the deadkey of the radio and want to maintain max swing without clipping the negative peaks.

all credit for this mod goes to Exit13.
LC

 

[Philomath]

Now I'm having a bad case of the rits lol. These radios are in pristine, out of the box condition, but old. I plan to leave them completely un-molested, Just the recap.
Like I said in the beginning, I'm not a tech, just a tinkerer.
but thank you, I will put your recommendations in the vault.

 

[loosecannon]

no need to mod these philomath, they are great with just a good alignment.

my message was for MKwrench who might want to try this mod out.
LC

 

[nomadradio]

Mileage is an issue. This type capacitor is commonly rated for some number of thousand hours of circuit stress. A barn find with 500 original miles is less likely to have bad caps than a heavily-used specimen the same age. Even if they are all good today, they will 'remember' how old they are a few miles down the road.

Circuit modifications are up to the user. I recommend choosing an objective before blindly changing components just to see what changes.

73