Electronics! Falling into the geek rabbit hole.

[highangle]

So the hum doesn't change with volume up/down? Do you have an effects loop and is it switchable? Sometimes they cause issues.
Inspect any case/frame/screw grounds that might be faulty. Find the power supply filter caps, if you can, and see if you feel up to replacing them.

Give any shop all of your observational data. Get an estimate. You may have a disposable amp.

[EWG]

So the hum doesn't change with volume up/down? Do you have an effects loop and is it switchable? Sometimes they cause issues.
Inspect any case/frame/screw grounds that might be faulty. Find the power supply filter caps, if you can, and see if you feel up to replacing them.

Give any shop all of your observational data. Get an estimate. You may have a disposable amp.

Effects loop is not switchable. Volume doesn't change the hum.

I'm thinking it might be the filter caps. Some local shops are telling me it'll cost between 100-200 most likely. I think it's probably not an option at that cost.

[highangle]

Meanwhile, a bag of Sanyo or Nichicon caps prob cost $3 on Ebay. No-clean solder's pretty cheep too. You can usually look up your existing cap specs by the codes on the side.

https://www.electronics2000.co.uk/da...f/capmarks.php

https://www.electronics2000.co.uk/ca...calculator.php

[EWG]

Meanwhile, a bag of Sanyo or Nichicon caps prob cost $3 on Ebay. No-clean solder's pretty cheep too. You can usually look up your existing cap specs by the codes on the side.

https://www.electronics2000.co.uk/da...f/capmarks.php

https://www.electronics2000.co.uk/ca...calculator.php

Thanks. I know literally nothing about this, but I may keep it around and fool around with it. To great frustration I'm sure.

[EWG]

Progress: Maybe there's more screwed up, but the hum is definitely coming from the filter caps. One of them is loose. If I move it around (to a pretty extreme angle) it makes contact and the hum goes away. Nice!

Except I have no fucking idea how to change a filter cap.

EDIT: well. I pulled the board, flipped it over, ham-handedly soldered the loose cap back on with a way too big gun and solder, probably barely connected it, put it back together, and it fucking works! Still get a bit of hum cycle-up and then drop away at start up, and still some static sometimes when no guitar is plugged in. Maybe just need to clean out input jack to get rid of the static?

Either way, pretty pumped!

[highangle]

Woot! Congrats on a successful re-flow!

You can pick up decent solder workstations with hot air and iron and an assortment of different tips for less than a C-note. Some will come with forceps and tweezers and mirrors - just about all you need for component swaps and buildouts.
A modern countertop convection oven can flow whole boards with paste solder. Paste and stick components on board. Pop board in oven. Heat to X temp and then turn off and cool down. When it's done, you have a populated board.
With a hot air wand, you can dab no-clean paste on with a toothpick, and flow tiny little components with a tiny little jet of air at just the right digital temp. Or you can heat & flow entire regions of a board at once with wide flat tips and more air.

Do you have a remote thermometer? They're great for finding faulty FETs and caps and resistors - one will be noticeably warmer than the others. That's typically how hard it is to diagnose a faulty MOSFET in a vintage receiver...


The Bob Noyces and Andrew Groves and other pioneers of electronics grew up on farms. Electronics is mostly common sense, and a lot more approachable than most ppl think.

[ghosthop]

Anyone with a preferred adjustable temp, bench top soldering iron? Almost all of my electronic experience is with mil-spec equipment from the early NASA days.

Right channel cut out on the hifi. One of my planned projects for this winter was to clean and replace circuitry from the 70s/80s. Looks like the timeline has moved forward.

Horowitz & Hill has been moved to the coffee table. Will be dropping hints to the wife that all I want for Christmas is an oscilloscope.

[basinbeater]

I use a hakko fx888d. I love it. https://www.hakko.com/english/produc...ko_fx888d.html

[basinbeater]

And for scopes, i think it is tough to beat the rigol $400 machine...
https://www.tequipment.net/Rigol/DS1...Oscilloscopes/

[highangle]

Hakko is a good brand...You prob want hot air too - "SMD Rework Station".

You may find you don't need to pay for pro-tier gear if you're not using it every day or week. These are not complicated machines.
Most of the Chinese stations that cost half or less of Hakkos and Wellers will last you a few years. Some are even cheap enough to buy for one or two jobs.

Tin the tips well, and they'll do a good in a wide variety of tasks. Zon and Ebay have most anything electronics. Ebay is a source for small quantities of pretty much any component you can spec, and old used and NOS shit too.

[basinbeater]

I've bought enough fake shit on eBay, that i discourage that path. Don't support the intl scammers. I do buy lots of stuff on eBay, but not electronic components. Don't support a Chinese ripoff of the hakko. Buy the good shit once, and have a decent seeing iron the rest of your life.
I've done lots of electronics repair and building, (i think it's fun), and i have yet to need a hot air rework station.
Just my experience.

[abraham]

I've heard decent things about the PineCil or TS80/TS100 for a portable unit. USB C PD seems like it could be good depending on your needs and other equipment. I think you probably could solder with power from you laptop, but I have been avoiding keeping up too much with the PD versions so I'm not certain. They are cheap enough I might pick one up, I figure it costs me ~$10 to go to my office to solder something if I didn't have a reason to be there anyway.

[unitofstuff]

I had an HSU Research VTF-3 Mk2 fall into my lap for free because it sounded "wrong." I hooked it up with the line level inputs (for some reason I don't have any subwoofer RCA cables around) and sure enough, it sounded muddy and scratchy but definitely had power. I pulled the amp plate and didn't see anything obviously wrong. I pulled the woofer and the cone and surround is in good shape, travels smoothly, and moves well with a 9v. I put a multimeter on it and it tests at 2.5ohms and rises to about 3.2ohms.

I'll try with the low level RCA inputs soon, once I can snag some cables. I don't know quite enough about this stuff to diagnose much more in depth without advice. Any words of wisdom?

[ghosthop]

Woosh. Really fell down the rabbit hole. KSL has been a source of great deals and met some interesting folks.

I picked up a Fluke DMM and probe master modular probes after finding my cheap meter bit the dust.

Next was an Aixun JBC copy after reading around eevblog. I agree with basin about not supporting intellectual theft but it’s a hard pill to support a $500 machine that fundamentally hasn’t evolved for a decade plus. I have been using the genuine JBC tips. Will need to replace the Chinese caps in the power section and add ESD protection at some point. Will most likely modify the iron stand to pass power to the handle at the same time to clean up the cord routing.

Have started cleaning 40 years worth of crud and am going to do a full recap on the preamp. Regulated voltages are a little funky so will check semiconductors after replacing electrolytics. Hoping to build a diy pcb holder using photography third hand next week.

I have had good luck sourcing solvents so far except DI water. Grainger will sell me a liter for $30 but I am thinking about poking around the chemistry building at the U with a backpack and helpless look on my face. I forgot how nice it was to have free access to those sorts of things.

[dunfree]

McMaster carr lists DI water for $5/ gallon, and they’ll give you a shipping quote online now.

[Thaleia]

If those options fail check if you have any local saltwater / reef aquarium forums or fb groups. Having a DI filter is pretty much a must for that hobby and some kind sole might hook you up.

[basinbeater]

Woosh. Really fell down the rabbit hole. KSL has been a source of great deals and met some interesting folks.

I picked up a Fluke DMM and probe master modular probes after finding my cheap meter bit the dust.

Next was an Aixun JBC copy after reading around eevblog. I agree with basin about not supporting intellectual theft but it’s a hard pill to support a $500 machine that fundamentally hasn’t evolved for a decade plus. I have been using the genuine JBC tips. Will need to replace the Chinese caps in the power section and add ESD protection at some point. Will most likely modify the iron stand to pass power to the handle at the same time to clean up the cord routing.

Have started cleaning 40 years worth of crud and am going to do a full recap on the preamp. Regulated voltages are a little funky so will check semiconductors after replacing electrolytics. Hoping to build a diy pcb holder using photography third hand next week.

I have had good luck sourcing solvents so far except DI water. Grainger will sell me a liter for $30 but I am thinking about poking around the chemistry building at the U with a backpack and helpless look on my face. I forgot how nice it was to have free access to those sorts of things.

What preamp are you working on?

[ghosthop]

Thanks all, I will pursue those leads.

What preamp are you working on?

Mitsubishi branded Diatone DA P10. I always wanted to put the full stack together (pre/amp/meter/tuner) but prices have left reality.

[basinbeater]

That thing is cool looking. You have a matching amp that "docks" with the preamp? Cool design.

[EWG]

Alright, got a question for you wizards. I have a Polk PSW505 that is making no sound. Everything seems to be functional on it otherwise. I'm going to pull out the speaker, check connections, run a multimeter on the speaker to see fi it's blown, etc. But here's the question, which might save me a ton of time: I guess some caps on these can go bad. If caps started to go, would it be silent or just make weird noises? On my guitar amps when caps go the sound just gets weird, it doesn't go silent.

Just trying to eliminate caps as the issue up front.

Edit: speaker tests correctly through the multimeter. Fuse is not blown. Plate amp recognizes a signal being sent to it since it switches from standby to active when i connect music through rca jacks. Just no sound.

[riser4]

The volume is turned off?