[R-390] Caps

[quartz55]

I think Justradios uses 'Dips' to avoid calling them by a trade marked name, but it can be misleading.

That said, I ordered some MLCC caps today.  RDER72J104K8K1C11B for the .1uF 630V, RDER72J103K2K1C11B for the .01uF 630V, and FK26X7R2J333K for the .033uF 630V.  I decided to go pretty much with what value was in the original circuit.  Although if I replace any of the 5000pf, I may just use the .01uF as Charles recommends.  I was sent some information about the MLCC caps, they are apparently surface mounts with a lead attached and coated.  So it looks like one must be very careful when bending the leads and soldering them in place to not stress the joint nor to place too much heat (250F max) on the wire to cap joint.  Another issue is the change in value with applied voltage, but looking at the charts, if we stay within 50% of max voltage, the change is less than 2%, so I'm not worried about that.  I may make a small fixture to heat sink and hold the leads in place while soldering.  Once in place they should be good, they should probably not be disturbed after installation.  I got more than enough for one radio and they only cost me about $25 including shipping from D-K.  The few ODs needed otherwise only adds up to a few bucks, so this should be a reasonable price to re-cap, plus it looks like it should open up a lot of space in the IF deck.

I'm still looking for some .01 to .047uF for the AF deck.  The OD 715P 400V .047uF ones I looked at are still too large diameter to fit on my board, unless someone has a number that will work, I'd appreciate it. It looks like the .01uF 400V will fit, they're only 9.5mm dia. I'll probably be using an external audio amp off the diode load, so it may be moot, but I might as well fix it.

I just went through what I think the voltages on the AF caps may be and this is what I get, C601 - 12VDC, C602 - 75VDC, C604 - 12VDC, C605 - 50VDC, C607 - 12VDC, C608 - 55VDC, C609 - 3VDC, so it appears to me that a 200V rating on any of those caps would be plenty, which would make it much easier to find an OD cap to fit on the board and not hit the chassis.  Correct me if I'm wrong or re-inventing things.

But I still need to finish the filters, I need to clean out my 8 and 16K, the 2 and 4 are ready for installation. I may have an extra 4K filter if it works when I get it back together.  I still have another 4K that is the older style shiny case to do, but they are going to come after the 8 and 16K ones so I can finish up one of my IF modules.

Then it's spring and there's too much to do outside, I've had a respite with the rain the last few days. I'm sure I'll be back on the Danuser post hole digger tomorrow.

Dave