Not sure if this forum is correct,
I’m having way too much trouble figuring out how to be sure I’m ordering the correct part. For instance I’m trying to build a P3A amplifier (Rod Elliott). Typical example: I want to order a 22k ohm 1/4 watt metal film 1% resistor. The lead spacing is shown as 10.16mm (.4”).
How do I read the data sheet to correctly identify this lead spacing?
There are always several parts available with the same description but different part numbers. Reading the data sheet to differentiate each is, for me, very difficult. I don’t see anything in the data sheet that corresponds to the required/suggested lead spacing. I’m a an older rookie trying to get through this.
Please advise
Part of the issue is that the recommended spacing doesn’t match up exactly with the data sheet. So I have to select the next size down which still has all other parameters correct.
I’m having way too much trouble figuring out how to be sure I’m ordering the correct part. For instance I’m trying to build a P3A amplifier (Rod Elliott). Typical example: I want to order a 22k ohm 1/4 watt metal film 1% resistor. The lead spacing is shown as 10.16mm (.4”).
How do I read the data sheet to correctly identify this lead spacing?
There are always several parts available with the same description but different part numbers. Reading the data sheet to differentiate each is, for me, very difficult. I don’t see anything in the data sheet that corresponds to the required/suggested lead spacing. I’m a an older rookie trying to get through this.
Please advise
Part of the issue is that the recommended spacing doesn’t match up exactly with the data sheet. So I have to select the next size down which still has all other parameters correct.
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Just wading through this myself, so totally not an expert source ... I don't understand what you mean by "I have to select the next size down which still has all other parameters correct".
Otherwise, TTBOMK, while the radial capacitors and transistors and things have lead spacing concerns -- I thought for most axial resistors with straight leads, you will bend the leads down with pliers (or a fancy tool) to fit the board, so it's sufficient that the length of the body is not longer than the lead spacing holes on the board (with some allowance for the bent leads). I have seen some big axial capacitors in pictures of crossovers where the length of the leads might be a concern, but probably not for a resistor.
So a YAGEO datasheet for a MFR-25FRF52-22K (22 kOhms ±1% 0.25W, 1/4W Through Hole Resistor Axial Metal Film) shows it is 6.3mm +/-0.5, so should be fine if the holes are spaced 10.16mm apart.
Where the Vishay Dale datasheet for the RN60D2202FRE6 (22 kOhms ±1% 0.25W, 1/4W Through Hole Resistor Axial Flame Retardant Coating, Military, Moisture Resistant, Safety Metal Film) shows length as 8.74mm (± 0.79) but apparently the coating could extend to 0.425" (10.80 mm), so might be tight.
Is that what you were asking?
Otherwise, TTBOMK, while the radial capacitors and transistors and things have lead spacing concerns -- I thought for most axial resistors with straight leads, you will bend the leads down with pliers (or a fancy tool) to fit the board, so it's sufficient that the length of the body is not longer than the lead spacing holes on the board (with some allowance for the bent leads). I have seen some big axial capacitors in pictures of crossovers where the length of the leads might be a concern, but probably not for a resistor.
So a YAGEO datasheet for a MFR-25FRF52-22K (22 kOhms ±1% 0.25W, 1/4W Through Hole Resistor Axial Metal Film) shows it is 6.3mm +/-0.5, so should be fine if the holes are spaced 10.16mm apart.
Where the Vishay Dale datasheet for the RN60D2202FRE6 (22 kOhms ±1% 0.25W, 1/4W Through Hole Resistor Axial Flame Retardant Coating, Military, Moisture Resistant, Safety Metal Film) shows length as 8.74mm (± 0.79) but apparently the coating could extend to 0.425" (10.80 mm), so might be tight.
Is that what you were asking?
Yes that was my concern and I appreciate the explanation. I’m not familiar with data sheets which has led to this frustration. The key is that the lead spacing on the pcb is what’s called out on the bom. So my reference to the “next size down “ is just realizing the actual meaning of lead spacing. My background is not great but just getting the right parts ordered has become a real challenge. Anyway, thanks for your help.
Just to be sure, the capacitors, transistors, terminal blocks, and other things do have lead spacing (and for capacitors diameter) specifications. To the extent that the BOM I was following was really off in a couple places and I literally spent most of my Saturday with a ruler on three PCB (one project) double checking those component values.
And the first time I ordered terminal blocks, I got the 2.54mm ones and should have gotten the 5mm ones.
And the first time I ordered terminal blocks, I got the 2.54mm ones and should have gotten the 5mm ones.
Measure the length of the resistor body you want to use, and add at least 0.2" (or more) to get the pad spacing for the pcb.
Larger resistors will need more added than smaller ones, especially if the lead wires are thicker.
If you use a lead bending jig, you can select an exact distance for the pad spacing, by the slot that you choose.
It makes every part repeatable, too.
https://tubedepot.com/products/1-4-1-2-watt-lead-bender
Larger resistors will need more added than smaller ones, especially if the lead wires are thicker.
If you use a lead bending jig, you can select an exact distance for the pad spacing, by the slot that you choose.
It makes every part repeatable, too.
https://tubedepot.com/products/1-4-1-2-watt-lead-bender