SX-450 recap - replace tantalum capacitors too?

[eedork]

I'm getting ready to start on an SX-450 recap using the BOM in this thread:

http://audiokarma.org/forums/index.php?threads/pioneer-sx-450-recap-need-parts-list.399302/

I noticed that this model is loaded with tantalum capacitors and am wondering if I should replace these while I'm at it. What's the general consensus - should these be replaced as well?

Note that after replacing some noisy 2SA725s with KSA992s the receiver works fine aside from some dead bulbs and a good thump at turn on.

Thanks in advance!
-Matt

 

[Watthour]

Generally, those tanatalum caps are a problem waiting to happen. Since the unit is already on the bench and the iron is hot, invest the few bucks in it now and rest without worry. Depending upon the value, stacked film poly or electrolytics would be safer and probably just as quiet or better.

FWIW, My original SX-450 has produced this power-on thump this since it was new in 1978. Both my SX-450s and the SX-550s I have produce that power-on thump. It can be minimized by turning the volume to minimum before powering down and when starting. These units have no speaker/protection relay, and by the design this surge is all but inevitable.

 

[eedork]

Thanks Watthour! I'll include my revised BOM here once I have the full list including all electroylitics and tantalums.

-Matt

 

[eedork]

Here's my initial BOM, including replacements (Nichicon KL) for all tantalums. I may have to sub Elna Silmic for a few values that are currently on backorder from Mouser. I also need to double check this list before placing my order.

Mouser QTY Value Voltage
647-UKL1H0R1KDDANA 1 0.1 35
647-UKL1HR33KDDANA 3 0.33 35
647-UKL1HR47KDDANA 10 0.47 35
647-UKL1H010MDDANA 5 1 35
647-UKL1H4R7KDDANA 3 4.7 35
647-UKL1E6R8KDDANA 1 6.8 16
647-UPW1E100MDD 4 10 16
647-UPW1H100MDD 1 10 50
647-UPW1H220MDD 1 22 50
647-UPW1E470MDD 6 47 10
647-UPW1V470MED 2 47 35
647-UPW1E101MED 4 100 16
647-UPW1V101MPD1TD 3 100 35
647-UPW1H101MPD 1 100 50
647-UPW1H221MPD 2 220 50
647-UPW1E221MPD 3 220 16
647-UPW1V221MPD 1 220 35
647-UPW1E471MPD 1 470 16
598-SLP472M050C5P3 2 4700 50

 

[eedork]

I thought I'd post a quick update on my progress. The recap is nearly complete! The only caps I have left are the few that are under the selector switch, which is going to be a pain. It looks like I'll have remove the switch entirely to get at them - I'm crossing my fingers that the switch comes out easily ...

So far this unit sounds really good! I plan on applying new grease to the outputs, installing new bulbs, and then doing a thorough cleaning before buttoning it up. This will make a great receiver for the garage.

The parts list I posted above worked out well for me although I had to substitute Elna Silmics for a few of the part numbers that were out of stock at Mouser. Since this is a low end receiver I opted to replace the tantalums with electrolytics to save a few bucks. Someone else may want to use stacked film instead. The last thing I'll mention is that if I were to do it again I'd go with a standard 25mm diameter radial capacitor instead of the snap-ins for the main filter caps. The snap-ins just barely fit, and I had to bend the leads a little to get them in.

-Matt