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1956-ish Silvertone 1335 1x15 Combo


Picked this up a couple weeks ago without any tubes, save for an old RCA 12AX7 in the preamp (upper chassis). It's nearly identical to the Danelectro Challenger 89, just in a different cabinet.
Started with cleaning it up, replacing the four PSU filter caps, removing the death cap, and replacing the power cord with a grounded one. Ramped it up slowly on the variac. It worked for a few minutes before the rectifier tube started arcing and the first two filter caps exploded. I think the 5Y3 I used was bad.
Got it working temporarily with diode rectification, but the voltages were way too high and the vibrato didn't work. The PT was getting pretty warm to the touch as well. It was also humming like crazy until I put my hand near the preamp circuit, then it would quiet down.
Most of the old carbon-comp resistors had drifted way out of spec, and I was sure at least a few of the coupling caps were leaking DC, so I bit the bullet and replaced every resistor and cap today with metal film resistors and orange drop caps. I also fabricated a shield for the back of the preamp chassis with some aluminum flashing I had in the garage and ran a dedicated ground wire from the lower to the upper chassis, instead of having all the ground current flow through the RCA cable shield. I threw a GZ34 rectifier in there and now it sounds great. Super quiet at idle. I've got another 5Y3GT on the way to get the voltages a little closer to spec.

Welcome back, Nate. Always wonderful to see your work.

Fuck yeah now THIS is the shit I missed!

Here's a quick rundown of what I worked on since March 2020:

GK 400RB: Bad volume pot. Sold for profit.

800RB: Shorted output transistor, likely counterfeits that somebody else put in there. Arcing power switch. Sold for profit.

Aguilar SL112 cabinet: Broken crossover PCB, broke the plastic mounting posts. Drilled new mounting holes and jumpered a broken trace and mounted it to the inside of the cabinet with nylons standoffs. Kept it for a couple months, then sold for substantial profit.

800RB: More counterfeit output transistors. I was able to rub the silkscreen off with my finger. Fixed and sold for profit.

Fender Rumble 200: Smelled like basement and cat piss and the knobs were covered in sticky gunk. Bleached the shit out of it. Measured DC offset going into the off-the-shelf Icepower Class-D module. SMD ferrite bead was getting hot under the thermal imaging camera and -15V rail was collapsing when the fan kicked on. Common problem on these modules. Replaced with a wire jumper. Ended up keeping this one for band practice duties, as it actually sounds really good and is pretty light.

Carvin BX700: This one was kinda rare, I guess. Never seen another one like it before. Active-clamp flyback power supply had a shorted clamp MOSFET. Spent a lot of time troubleshooting this one before shotgunning a bunch of parts into it to get it working. Ended up finally buying a cheap hot-air rework station also. Sold for a small profit, after considering all of the time I spent on it.

Ampeg SVT-3 PRO: "Partially working." Just needed the output transistors rebiased. Common problem with these. Replaced three broken EQ faders also. Took about 2 hours total, sold for profit.

JBL 306P MKII:
Sold my JBL 708P studio monitors (for over double what I paid 3 years ago) and bought a pair of 306Ps instead, for 1/10th the cost. The 306Ps are definitely in the budget category, but they get you about 80% of what the 7-series does.

I really liked the 708Ps, but they were slightly too tall on my stands, so the tweeters weren’t at ear level. They’re also designed for more mid-field listening, from about 10 - 12 ft away. My desk is set up for nearfield.

A common complaint with 3-series is the resonance around 240 Hz that makes them sound a little boxy. People have tracked it down to cabinet resonance, and adding internal bracing helps. I cut a couple of dowels and glued them in there.
I also added mass to the plastic front baffle with some fire putty (basically non-hardening clay) I had left over from building the studio in Nashville. Then I filled in the chambers with siliconized latex caulk, the heaviest I could find.
I stuck some Peel & Seal (the hardware store equivalent of Dynamat) to the metal backplate to damp the ringing of the thin panel. In total, I added about 3 lbs to the whole speaker, or about 20% more mass.
I did one speaker first, then set up a blind A/B test to see if I could tell a difference with the unmodified one. Bass is tighter, less boomy, and a frequency sweep sounds less peaky.

Orange OR15: “No output” Well, yeah, there’s not going to be any output when the HT fuse is blown. So I replaced that. Somebody also attempted to install a Mercury Magnetics output transformer, but they had their primary side wires mixed up and it was only outputting about 350 mW before clipping. Swapped the wires and cleaned up their horrible soldering job and everything’s working now. Sold for significant profit after an hour of work.

Another 400RB: Cold solder joint on master volume pot. Sold for profit.

Another SVT-3 PRO: Blown output transistors. Sold for profit.

I also completely redid another drum kit, but I'll save that for another thread.

tallchris wrote: Wed May 05, 2021 5:25 pm Fuck yeah now THIS is the shit I missed!

That's what I'm talkin bout. What up my dudes.

Nate Dort wrote: Wed May 05, 2021 7:31 pm Here's a quick rundown of what I worked on since March 2020:

Sold for profit.
Sold for profit.
sold for substantial profit.
sold for profit.
Sold for a small profit
sold for profit.
. Sold for significant profit
. Sold for profit.
Sold for profit.

see you in hell

supply and demand, my dude

I think the main takeaway from years of fixing and flipping gear is that the majority of failures are due to user error.

scrotescape wrote: Thu May 06, 2021 10:41 pm

Nate Dort wrote: Wed May 05, 2021 7:31 pm Here's a quick rundown of what I worked on since March 2020:

Sold for profit.
Sold for profit.
sold for substantial profit.
sold for profit.
Sold for a small profit
sold for profit.
. Sold for significant profit
. Sold for profit.
Sold for profit.

see you in hell

I would expect that if you bought something, then fixed it that you wouldn't sell it for what you paid for it. It wasn't working, you've used your knowledge, skill and experience to make it work and you've sold it for its new value. Otherwise what happens? Landfill? You can sell something for a profit and even a substantial profit without ripping someone else off.

I have received broken gear for free loads of times from people that couldn't be bothered to fix it or have it fixed by someone else. It was worthless to them - but to put that gear back into service adds significant value to it. I wouldn't expect someone to get it for free because I did but I also wouldn't try to rip someone off and sell it for more than it was worth.

Nate Dort wrote: Fri May 07, 2021 6:33 am supply and demand, my dude

I think the main takeaway from years of fixing and flipping gear is that the majority of failures are due to user error.

Emphasized for necessary and unnecessary parts

Speaking of user error...

I dove into repair and rebuilding more during the pandemic than I ever had before, but there was one repair that I was quite proud of. I really fucked up my Tascam 488MKII. I've been through a lot with this thing and have had it apart countless times, but I did something really stupid. I was trying out an old PRO CO DI box that said it could be used as an interface between the speaker out of an amp and a recording console. I read up to make sure this was correct, and found evidence that it was. But when I hooked it up, I used the 1/4" output from the DI which I did not realize was a bypass that ran straight off the input. So I hooked up a tube amp directly to an input of my Tascam. Within 30 seconds I realized my mistake, but the damage had been done. All meters were dimed and there was a squeal coming from the headphones even after disconnecting everything. Then it started to smoke. I almost cried. Anyway, I sucked it up and took it apart the next day and identified a burned and blistered IC on the channel strip that the amp was hooked up to (it was a NJM4565LD) and I ordered 2 NOS chips from ebay. I used my fancy new desoldering station and removed the IC. It was tricky, there was a little bit of trace that lifted around one of the legs, but I got the new part in and measured continuity where it needed to go. Put everything back together and now my 8 track lives again! I still use it almost every day. That was a big repair for me.

I also bought another one from Japan for cheap because it would do everything except engage the 'record' function. After much trial and error it ended up just being the reed switches that sense the tape/tape tabs. They were bent a bit out of tolerance, so after what amounted to a lot of unnecessary swapping of buttons and switches on the board, all I had to do was gently bend the arms of the reed switches. Wahoo!