Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Filter Can Restuffing for Valco Amp - Completion

I got the new capacitors from Mouser and I'm going to restuff the can. Glad I measured them and ordered more or less by size. This is the smallest can cap I've done and everything was a tight fit.

I've written about this before, but here is is again in case you missed it the last go-around.

Drill some small holes in the base of the can. One for each of the positive tabs and one for ground. It's a good idea to do some planning beforehand, especially for the ground hole.

In the past, I've said something like "thread the positive leads through their respective holes near the tabs." Here's a picture. This is the first capacitor's positive (+) lead being pulled through. I just bend it and wrap it around the tab. It will get soldered later when it's back in the amp and everything is being reconnected.

Here's that planning I mentioned.

I'm putting a 22 uF cap in the first section. Originally, the can had 10 uF, but modern caps are so much smaller that I was able to double the capacitance. I think 10 uF is pretty skimpy.

So we have the 22 uF cap with its leads going through the base of the can. You see one of the 10 uF caps (there are 2) lying next to it while I figure out exactly how it will go above the first cap.

The leads won't reach on their own, so I solder a piece of component lead onto them so they'll reach. When I build or work on stuff, I save clipped-off leads for this very application.

Here are all three capacitors installed.

The bottom cap - the 22 uF one - has its ground lead running through the can's bottom to one of the ground tabs. Then I ran a wire up toward the other 2 caps' grounds and soldered them together. So we have all of the grounds running to one point.

The positive leads run down through the bottom of the can and connect to their respective tabs. See the green heat shrink? That's covering those leads.

You may say, "Mr. Crawfish Man, why don't you just tie the grounds to the can itself?" That's a good question. The answer is that the can is aluminum, and hard to solder to. So I just use a tab instead. I also like the idea of just one ground point.

A final test run to make sure it all fits.

This one was fairly tight, as I mentioned, so I used some electrical tape to hold the cans together and doubly insure nothing could work loose and touch the can by accident. Not something I usually bother doing, but this was a little different than usual.

Mix up some JB Weld and put some on the mating seams on the can. Reminder to self: you are now out of JB Weld. Get more.

Line the can top and bottom back up and gently clamp the can in a vise to dry overnight.

If your cut was clean, and you've lined the seam up well and you clean up the excess epoxy, the seam will not be visible from a distance.

Congratulations! You've saved a vintage Sangamo capacitor can from extinction.

There's one more electrolytic capacitor I'm going to change before I fire up the amp. This is the first section cathode bypass on the 6SL7 preamp tube.

You can see the old cap alongside the modern Sprague I'm replacing it with. The Sprague is rated for 50 volts versus the 25 of the original, yet it's still much smaller.

Good thing I made a layout drawing of the filter cap connections, huh?

I also put a modern 3-prong grounded AC cable on the chassis. I don't like the way the AC line has to run across the amp, so I raised it up out of the way as much as I could.

Here's the reconnected filter cap in the chassis.

Couple of notes here: the blue arrow shows the grid (signal) line to the output tube from the preamp tube. I'm eventually going to move that coupling cap (red one on the left) over to the output tube grid. I'll also run a shielded line here instead of an unshielded wire.

The way this is wired leaves it open to pick up hum and noise. You'll see it runs right across the amp under the high current filament lines off the transformer. It's just poor wiring layout.

The other change I'll make is at the green arrow. This is the 6 volt filament line for the preamp and power tube. It's not dressed properly - it should be a twisted line. Easy to correct, and again, it's an anti-noise measure.


Restuffing Can Filter Capacitor on a Valco Amplifier

I have this old Valco amplifier chassis that I'm going to recap. Should be a pretty easy project I think.

If you do a search for "Valco" or "Supro" on that famous internet auction site, you may see some amps listed for sale which have this same chassis.  I don't know the model number, since there isn't one printed on it!

It seems Valco made a few variations of this amp.  This particular variant has a 6SL7 preamp tube, a single 6V6 output tube and a 5Y3 rectifier.  You can also see it has three inputs - two labelled "instruments" and one labelled "microphone."  It also has volume and tone controls.  It probably puts out about 3.5 watts or so.

I've seen a similar model, but with a single volume control and with push-pull 6V6s, and I believe there is also a version with the same push-pull output stage with both volume and tone controls.

I did find a schematic on the interwebs which seems to be the correct one for this amp, but it's so darn simple that it's pretty easy to follow.

True point-to-point wiring, just a couple terminal strips to connect stuff to.

I really like old tube sockets that have the tube type printed right on them.

Note the use of rivets to mount the sockets too - no nuts and bolts here.  Cheaper to build this way.  And probably less labor intensive, if you think about it.  Save those pennies where you can.

The AC cord is a 2-prong one replaced many years ago.  You see the splendid replacement job - instead of running the lead through the hole in the tab, our repair guru just soldered it to the tab, and also saved money by using as little solder as possible.

I'll replace that cord with a modern 3-prong grounded cable.

Here's part one of the restoration: unsoldering and removing the can capacitor.

I use desoldering wick to get the old connections off the filter cap can.  Make a drawing of what goes where so you won't forget later and blow everything up!

Everything's disconnected from the cap terminals.  Now I need to unsolder the mounting tabs from the chassis.

Sometimes you see these tabs soldered and sometimes you don't.  Fender is famous for using massive quantities of solder on these things.

In any event, I need my big 175-watt soldering iron to melt the solder blobs in order to remove them.

That iron gets super hot and requires a lot of care while maneuvering it around.  It's easy to touch something you don't want to touch and burn or melt it.  That includes your fingers.

Here's the solder removed from the can's mounting tabs (green arrows).  Untwist the tabs to straighten them out and the can can be removed from the chassis.

Here we have the can after removal.  I left those 2 resistors on for now.  I want to replace them with modern 2 watt versions, so I need the old ones as a reference.

It's not really necessary to change them out, but the old ones are rated for 1/2 watt, and I like the peace of mind of bigger ones.

The last time I opened up a can like this, I said I was going to try using a pipe cutter.  I've been using kitchen knives for this lately.

The pipe cutter works ok, but it leaves a bigger seam I think.  This can is actually fairly small in diameter (about 7/8 or an inch or maybe 20mm), so the pipe cutter was a little tricky to handle - it kept slipping off, so my cut wasn't the cleanest.

I'd like to try the cutter on a bigger can to see if it actually works better or worse than a knife.

Anyway, here's the freshly opened can.

I just hack the innards off the base.  Use gloves to handle the innards.  There are no PCBs there, but it's still not something you want to touch with your bare hands.

I save the innards in a container and then take them to my local dump and put them in the hazardous waste disposal.

In addition to the actual capacitor innards, there was some tar in the top of this one.  I believe this stuff was used as both an adhesive and as a moisture barrier.

I scraped it out because this can is small and I'm going to need all the space I can get to mount new caps.

New caps...umm...yeah.

The original can had 3 10uf @ 450 volt sections.  I figured I'd put a 22uF in for the first section for some extra filtering, and then two 10 uFs.


The caps I have on hand are too big!  Even 3 10uFs won't fit.  First time I've had this problem, but as I say, this can is narrow.

So I went to the Mouser site and ordered up some smaller ones that will fit.  So I'm in a standstill for a couple days until I get my new caps.


Record Cold Reading

Record cold on the SAABmarine outside air temperature gauge this morning.  That's the lowest I've seen since I put the gauge in the car 8 or 9 years ago.

Zero degrees F!  That is about -18° C. It was windy, and with the wind chill it was -22° F, or -30° C.


Filling Too-Deep Guitar Nut Slots - on an Ebony Nut!

I was playing my trusty 1931 Martin 0-18T guitar the other night when I noticed it had a slight buzz on the open G (3rd) and A (1st) strings.  The nut slots were cut very deep and now with the drier winter air, the strings were just touching the top of the first fret.

What I need to do is fill the nut slots and recut them.  I've done this one bone a lot, but I think this might be the first time on an ebony nut.

The process really is the same.  I took a hunk of ebony I had on hand, leftover from making a bridge on this same guitar,  and I filed on the edge to make some ebony sawdust.

You could use sandpaper to do this, but you'll find you get sandpaper bits in the sawdust.  Better to use a file I think.

Then sprinkle some of the sawdust into the nut slot in question - here it's the first string's slot - the high A.

All of my pre-war Martins have ebony nuts.  If you think about, ebony makes a good material for nuts - it's hard and dense for good tone but yet it's still easy to work with.

I don't know if Martin used ebony exclusively during this time frame, but I know I've seen a lot of Martin instruments from this era with ebony nuts.

You see that I put some tape on the guitar to protect it during the next step.

As with a bone nut, we hit the ebony dust with a drop of thin CA (super) glue.  I'm using a dropper to get the glue in the slot and not all over the guitar!

Then let it dry for 5-10 minutes.

After the ebony fill has dried, you can use a nut file to deepen or recut the slot as needed.  Or leave it as is.  Whatever is needed.

Slots filed a bit and strung back up.

The slots are deep and wide on this guitar, so it actually took me a few attempts to get the depths just right.  I find that on tenor guitars with a short string length (I think this one is 23 inches), and therefore a more 'flexible' string tension than a standard guitar, you can't go quite as low on nut slots.

Now back to practice!


Stereo Install in SAAB c900 Complete

Well, I finished the stereo install, put the seats in and the whole thing works!

I was moving quickly so I didn't get a lot of pictures, but most of the assembly was just the reverse of disassembly.  What I did was get the console back in, with the new stereo head unit in it.  Then I wired up my new Rockford-Fosgate amp, tested that the stereo worked, and then put the seats in.

So here we go.

Here's the console going back in.  I had a thought at one point that I should fasten the bottom half to the top half and put it in as one whole unit.

Good thing I didn't.  Just as with removing it, you need to do a bit of maneuvering to get it in place...this is during the process.

I have to say that most all of this work was so much easier with the seats out - lots of room to move around.

You may recall the plan was to put the stereo into the DIN-sized slot in the lower console that formerly housed a storage bin.  And that's what I did.

This is the back side of the stereo head unit.  It looks like a jumble of wires (and it is, I suppose) but it's not too bad.

From the top left: the blue arrow is the antenna lead from the stereo.  It runs down to the bottom bin of the console, where it connects to the factory antenna lead.  It actually connects to an extension lead, since the factory lead is short and ends up behind the factory radio location high in the dash.  So the extension connects the factory lead and the stereo.

The red arrow points to the component connectors that run under the carpet and back to the amplifier.  This end goes the the preamp out on the stereo.  I used Stinger interconnect cables and I really like the looks of them - nicely made with a lot of shielding.

The green arrow points to the Kenwood connector.  This is the connector that carries 12v into the radio and also has the illumination, dimmer, and speaker leads.  The connector is the radio end of the harness I made up that connects the radio to the factory plug in the dash with the same connections.

The brown arrow is for the rear USB port.  I ran this out to the front of the console.  There are 2 USB ports on the stereo - one on the face and this one.  You can access files from a USB drive or iPad, etc., via these ports.  Wow.  How modern.

And the grey arrow is where the Bluetooth microphone connects.  I decided to hook it up and run it to the front of the radio in case I ever use it.

After I got the console in, I went down to The Dungeon and prepped the big cables for the amplifier.

Both of the cables are pretty large - 4 gauge.  You can see how thick they are - about 9mm or almost 3/8 of an inch.  They're so thick, in fact, that my tin snips wouldn't cut them.  I used a small razor saw to cut them to length.

The amp needs at least an 8 gauge cable due to the power it draws.  I figured I'd just go a couple sizes larger to be safe...and in case I ever were to need that large of a cable.  I don't want to do this wiring again.

Here's one of the terminals I put on the cable - this one will be the ground end.  They are crimp terminals, but I crimped and soldered them for an extra measure of reliability.  I used my 175 watt iron to solder them.

Here's a test run for the ground.

The bolt is one of the bolts that hold the passenger seat in.  It's fairly large, and with the weight of the seat on it, will not shift.

I just ran it under the carpet and up to the bolt.

Here's what it looks like with the carpet down - pretty tidy I think.  Although no one will see this once the passenger seat is back in.

This is a view looking down at the amp after connecting it all up.

This is on the floor under where the passenger seat is.

The wiring from the far left is the ground, the turn-on lead from the stereo, and the B+ (12 volt hot) from the battery.

The other connections are for the 4 speakers, and the interconnect cable from the stereo.

I mounted the amp on a piece of 1/2 inch plywood.  It's bolted to that, and once I get all the settings on the amp correct, I'll semi-permanently attach the plywood base to the carpet with heavy-duty Velcro.  (There are some settings for bass boost and filters that I'll play with over time, so I need to have access to it in the short term).

The big fin on the top of the amp is a heat sink - it needs 1 inch of clearance.  I'll have about 5 inches of clearance under the seat.

The last bit of wiring is to connect the B+, or hot, lead, to the battery.

You can see the blue cable that runs to the positive terminal on the battery.  That cable runs up to a fuse holder that's mounted to the side of the engine compartment.  That's the fuse for the amp - 50 watts.  Then the other end of the fuse runs to the B+ cable which goes down the fender, and into the car, under the carpet and to the amp.

You can see why I did all of that wiring beforehand - I routed it where it worked best, and now I just connect everything up!

And guess what?  It works!  :-)

I really didn't expect any problems, but you never know!

It's so much easier to have the luxury of making assemblies - such as the radio harness - that will pretty much ensure everything is done right.

So then I put the seats back in - about 8 weeks after I took them out.

The passenger seat works great.  I did some work on the driver's seat to untwist the back, but I'm looking for a better one to replace it.  The seat bottom and back are not in good shape.  But it's functional for now.

Here's a shot of the dash with the new gauges and the stereo in place.

I still need to hook up the oil pressure and water temp gauges.  I'll do that in a couple months when the weather is better.  The wiring is already in the engine compartment, so that should be straightforward.  And I want to get a dimmer for the gauges - they have LED lighting and they're TOO bright!


Car Stereo, Amplifier and Gauge Wiring on the SAAB c900

I'm relocating the stereo from its position up high in the dash to down in the center console. I got a Metra adapter for my new Kenwood stereo (Excelon X-998) which will adapt the Kenwood plug to the Saab factory plug.

Here's the harness I made with the Kenwood plug at one end and the Metra (same as the SAAB female plug) at the other end. Basically you connect the B+, ground, lighting, dimmer, etc., wires on one to the equivalent wires on the other. It's nice because I like to solder wires together whenever I can, instead of just twisting them together and using wire nuts.

Here's the radio connector end. Kenwood puts labels on the wires so you know which is which - and then you just connect them to the Metra adapter's wires for the same functions.

I also tapped out the B+, ground, and illumination wires at each end. I'll use these at the radio end for a map light and an outside air temp gauge in the future.

On the other end, which will be up behind the dash, I'll use those wires for the voltmeter and the gauge lights.

I decided to go with Autometer gauges this time around rather than VDO. Just a change.

I'm putting a voltmeter and mechanical oil pressure and water temperature gauges in the DIN slot at the top of the dash formerly occupied by the radio.

On my other 900, my gauges are in the same location, and they point straight out. This time I decided to angle them toward the driver (also known as me). Autometer sells a set of mounting rings that will let you angle them on a horizontal or vertical (or both) angle.

You can see in the picture above, they'll stick out a bit, so I trimmed them at certain spots so they'll slot into the dash properly. We'll see that after they're all installed.

For some reason, I forgot to take a picture of the harness I wired up for the gauges. At any rate, you can see some of the wiring here...the gauges are wired into the radio harness taps for 12v and illumination, which actually come off the car's factory plug.

Other than three small wire nuts which were unavoidable, every connection on the stereo, gauges, and speakers are all soldered or have connector plugs for good reliability.

I was actually running the front speaker wiring when I took the shot above. You can see my helpful "hole for wiring" finder (aka Mag-Lite) pointing into the DIN slot. Shine a light in and you can see possible places to run a wire.

The oil pressure and water temp lines have to go into the engine compartment. This is the water temp sensor, which is permanently attached to the gauge via a stiff line. The blue bolt is 7/8 of an inch (about 20mm) around, so we need to drill a fairly big hole to run this thing through.

I was ready to drill a hole with a hole bit when I discovered this existing hole and grommet running from the driver's side kick panel into the engine compartment.

It will be large enough the run my gauge sending lines through! Whoo hoo.

Note the factory grounds - more proof this car was built by human persons. Say no to robots. Just say no.

I popped out the grommet and opened up the center to get more room for the 2 new lines to run through. I also had to slit it so I could get it out and back on.

New lines in place. I was still messing with getting the grommet fully seated at this point, but it is back in the hole as I write this. (It will keep the lines from chafing on the sheet metal if they move around any).

The larger black hose at the top is for the water temp, and the white nylon hose is for the oil pressure.

This worked out well - no new holes had to be drilled.

Here's where the new lines wind up. They come up from the corner of the firewall and up near the fuse box.

I'll eventually tap into the water hose that runs from the engine block to the "in" on the heater. The oil pressure gauge will tap into the threaded hole where the oil sender currently lives.

I'll finish that up when the weather is better, but I needed to get the wiring all in place while I had the dash apart.

Back to The Dungeon to finish up the last part of the speaker install - the front speakers.

Here are the two old speakers - you don't need a sharp eye to see they were different! One was a Pioneer TS-A1090 and the other one was a JBL GT42TO.

I'll keep them for future experiments...bwahaha.

The new speakers are nice Focal 4 inch models with adjustable (rotating) tweeters. This one is about the go into the dash opening. You can see the 2.2uF crossover capacitor and coil right on the back of the speaker.

I'm putting an amplifier under the passenger's seat. So I ran a 4 gauge cable from the battery through the passenger side of the engine compartment, along the same path as the old factory speaker wiring.

You can see that old wiring in the white box running along the sill.

There's a big 'glove' rubber grommet between the passenger side kick panel into the engine compartment. Cut a slit in it to run wiring into the engine room. Easier than the driver's side!

Here's all the stereo wiring ready to connect to the amp.

You can see the B+ cable, the speaker wiring, the interconnect cables and the power amp turn on wire.

I kept the B+ away from the others as a hum-reducing's the amp builder in me :-)