Dial lamp replacement

[sKiZo]

Deserves a sticky I think, considering some of the convoluted "Chinese Puzzle" hoops they make us jump through to get er done. Normally, the fuse lamps will still work, but go intermittent due to cracking solder joints on the lamp holders. Too many hot/cold cycles over time, and it happens.

My bad if there's already a sticky on the subject ... point me to it and I'll update with mine. If this DOES become a sticky, please keep t If yall like, post yours up, and (assUming the new forum software allows it, I'll link to that in this post as follows:

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Couple notes: DO plan to replace all the fuse lamps if you've got one that's burned out. Lumen output can be quite different based on who made them and when, even if they're all the same voltage rating. Worth noting, it's difficult to find exact replacements for the 7 volt lamps Sansui used in a lot of their equipment, and your choice becomes either 6v or 8v. I shy away from the 6v as those do heat more and can damage the bulb holders as well as stress the bulbs for early failure. the 8v replacements ARE slightly dimmer, but work quite well. As mentioned, replace the lamps as a set for an even glow across the dial.

DO use a gentle touch ... the lamp cages CAN fight you, but once you get them aligned properly and get everything out of the way, they should slip right out. Haven't found one yet that required any desoldering - Sansui was nice enough to provide connectors where needed.

One other reason for a gentle touch - these light boxes can get fragile over time from the heat of the lamps and break quite easily. Don't say I didn't warn ya ... Don't worry about discoloration - no cure for that I'm aware of. A tip for lamp removal ... Slide a garbage bag tie under one end of the lamp and use that to pull that end out gently. It will swing right out the other holder them.

 

[sKiZo]

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This one was a puzzler, hence this thread. Seemed as if nothing short of blasting caps would get me to the circuit board the lamps are mounted on.

Step 1 - Remove the fascia. That was pretty straightforward.
Step 2 - Loosen the two mounting screws for the light box located at the top corners. Don't remove these - the box is slotted so it should slip right off when you get that far.
You'll see two slip connectors just behind the light box to the left. Remove those. No need to mark them as there's only one way they'll go back on.
Step 3 - If you look at the back right corner of the box from the front of the receiver, you'll see a small vertical board. This needs to be removed so you can slide the light box far enough back to clear the chassis. One screw to the right of the board and it lifts off a slip connector. Plenty of wire to be able to swing the board out of the way now.
Step 4 - Not as obvious, but you also need to remove the 2/4 channel indicator light. Two screws at the base, and that lifts right out as well.
Step 5 - Here's where it gets tricky. There's a secret spot that's hard to describe that allows you to swing the box out for access to the lamps. Best I can say is, work the whole thing to the left a bit and pull it back as far as possible. It will still want to hang on the chassis, but there's one special place where it magically clears and pulls out.

Here you can see the two slip connectors I mentioned, as well as the small circuit board and the 2/4 channel indicator.

If you're just replacing lamps, that's as far as you need to go, but ... with as much trouble as it was to get this far, might as well go the extra step and resolder the back of the board. If the lamps aren't intermittent now, they will be eventually. With no further disassembly, you can rotate the light box for access to the circuit board. It will fight you a bit, and there's only one way to do it right without stressing the wires, but it can be done. I set the chassis vertical and propped the board away a bit to allow good solder flow to all the connections. That leaves you with this:

I hit each fuse holder with a desoldering tool, and reflowed them with a HOT iron. Lot of bulk on the holders, so you want to heat the tabs first, then slip the iron down to the copper pads. This minimizes any chance of lifting the copper off the board.

I also reflowed all the wiring for the mode indicators. Had a couple that didn't "feel" right, and sure enough, a slight tug broke the connection. Stress during removal of the box I expect. Anyway, good check to make as you go along.

Once done, I swung the box back into place enough to be able to reinstall all the connectors, fired it up and double checked all the lamps, then let it go for a couple hours to make sure the intermittent issues were fixed. Better then than later, right?

Assembly was pretty straight forward. Couple notes ... The dial string - Pinch that between the box and chassis and you could weaken or break it. Best avoided, so careful does it. Also, if I were to do it again, I'd also add a layer of metal duct tape under the separator for the indicator lamps ... I do notice a very slight light "bloom" from those in the dial area if I'm sitting in the dark and feeling exceptionally anal retentive ...

PS ... while you're in there, might as well clean the controls, but that's another thread ...