Two great pulls from the scrap heap

[Tubetec]

So today I took a trip to the recycling yard with a few electronic odds and ends ,
Low and behold I dug out two old style linear benchtop PSU's ,
Model 6305 and 6306 , one single rail upto 60volts ,
the other a dual rail supply upto around 30 volts ,

There both 110v volt units , just as well I picked up a 230 to 110 volt autoformer recently from the same free source ,

So the units had been out in the rain for a few days , and there was signs of moisture ,
I dusted it out and the PCB cleaned up nicely , there was some other corrosion visible on the main heatsink , again that was easy to clean ,
I set it up with a hair dryer pointed at the transformer , left it around an hour to make sure any moisture had evaporated from the windings ,
So plugged it in and worked , max output voltage is a little lower than expected at 48 volts , but other than that its rock solid ,
I set it for 14.6 volts and sure enough an hour later its only deviated 0.1V , thats from a cold start , the first time the units been powered up in years most likely .
Its on soak test now , we'll see how it goes .
I wasnt able to test the second unit yet , but I've every reason to believe its working ,
The gear was badged M/A Com , who had a production facillity here back in the old days , I think they still have offices here today .

Theres a couple of other bench multimeters down there too including a HP , I think Ill take a trip back down and grab them ,

Back in a bit ,

 

[rock soderstrom]

Good find Snap some photos.

 

[cyrano]

Congrats, good catch!

I was at the dump too. Fortunately there wasn't anything interesting in the container for glass...

 

[Tubetec]

As well as the two HP psu's models 6205C , 6206B
I got a HP 3478A bench meter without its fuseholder so I can test it yet ,
And a Blackstar inteligent multimeter with 5 digits , that has a cal error , but does power up .

I also happened to meet the owner of the yard as he was leaving ,
He said I can take away what I want ,only rule is no computers , due to data protection .

 

[rock soderstrom]

premium recycling yard

 

[Tubetec]

Ive had the single rail HP on all day , initially it seemed to be limited to 48v and go no further but after a few hours on I checked again and it now goes all the way to 70 volts ,as it should .The moving coil meter is accurate ,voltage stabillity is very good but noise levels are out of spec , it should be less than 0.2mV with a small load , even with no load Im seeing around 0.6mV .

 

[AnalogPackrat]

Nice score. Your 6205B looks to be late 60s to early 70s. I have an early 1966 6205B (has Harrison badge) that I got for $50 semi-functional. Recapped it and it's a solid supply. Your 6206B looks to be an 80s or later build. If that 3278A is working it's a very nice meter. I'd love to find some dumpsters like that.

 

[MidnightArrakis]

Maybe there needs to be a "Dumpster Diving" thread on here!!!

As a teenager in 1965, I climbed into a large "Goodwill" container that was stationed in a local strip-mall parking lot and found a still-working oscilloscope!!! I took it home on my bicycle, cleaned it up, put a new AC-cord on it and began my journey into electronics. Another time, I climbed into the "Goodwill" container and found a shortwave radio that someone had ditched. I also got that to be working and I have been "hooked" on listening to -- W W V -- ever since!!!



/

 

[ruffrecords]

When I was about 14 (back in 1965) I joined the local ham radio club. The club secretary ran a TV shop and repair business from a nearby town. There were a few of us youngsters in the club but we had very little money and could not afford to buy all the parts we would need to build ourselves a receiver (we certainly could not afford to buy one). One day the secretary invited us round to his house and took us out into his back yard There, in the middle was a pile of old TV chassis maybe 10 feet high."Help yourselves, lads" he said and armed with a screwdriver and some cutters we grabbed ourselves a good pile of resistors, capacitors, valve bases and so on.

Cheers

Ian

 

[Disco Volante]

I rescued a Tek 317 from the electronics recycling in Copenhagen years ago. They threatened to call the police, but there's no way I'm not rescuing a Tektronix! And it's so cute! Still have it, still works, though it needs a new fan...

Cheers, V!

 

[chrispbass]

When I was about 14 (back in 1965) I joined the local ham radio club. The club secretary ran a TV shop and repair business from a nearby town. There were a few of us youngsters in the club but we had very little money and could not afford to buy all the parts we would need to build ourselves a receiver (we certainly could not afford to buy one). One day the secretary invited us round to his house and took us out into his back yard There, in the middle was a pile of old TV chassis maybe 10 feet high."Help yourselves, lads" he said and armed with a screwdriver and some cutters we grabbed ourselves a good pile of resistors, capacitors, valve bases and so on.

Cheers

Ian

Great anecdote Ian. Today I’ve picked up a transit van load of musical gear from a friend who’s clearing out a repair shop. He’s been exceptionally generous over the last few months and I’ve been the benefactor of some really good stuff in various states of repair. My GF runs a non for profit org that does a lot of musical based activities, so I’ve been fixing all manner of amps and the like to help out with her project.

I’ve also been helping my friend build a Hairball 1176 blue stripe over the last few weeks. Yesterday we completed it and just needing to calibrate it on our next session. I’ve got a little Tenma signal generator and it wasn’t up to the job of giving a 0dBu signal with the loading of the input stage. Anyway, today, along with the van load of gear, he just happened to ask me if I needed a signal generator. Funny how the world works and I came home with this.

 

[oldskool1]

I am in Los Angeles. I can't believe what people bring to the electronics recycling place. They throw out computers that are years newer than the ones I use to make a living. I've seen SSL4000 channels and parts, AVID gear, huge lighting consoles in great shape, as well as all sorts of working and almost new electronics. And it makes me angry, because they won't give you what's going to the shredder anyways... they want to charge top dollar for it! It's so LA. Makes me sick.

 

[Brian Roth]

damn....bummer....

sigh....

Bri

 

[Disco Volante]

The amount of perfectly serviceable electronics being scrapped is a part of what's destroying our habitat. Sigh.
I'm mentoring a friend's son, he's a born tinkerer. We need people like that,-)

 

[Tubetec]

Just digging into the service documents on the HP psu's ,
theres a lot of extra functions possible by changing jumper connections on the back panel , current or voltage drive , with external sense wire etc .
HP's service docs are legendary , written in the most concise language ,
with a full overview of circuit opperation .


The abject waste of resources is truely horrific , then profiteering off the back of it .......

As I said I met the owner of the local yard on my trip down the other day , the place is under 10 minutes walk from my house , so I'll be dropping off my empty beverage containers every couple of days and seeing what the scrap heap has to offer .
I must remember to bring a pair of gloves next time though , otherwise I come back covered in cuts and scratches on my hands and I end up having to clean my own blood off the equipment later


I found the nicad 2.4v back up battery in the Blackstar meter doesnt take or retain a charge , it seems like its probably worth the effort to try and fix though ,
I was able to get the service info and access the cal function , so theres every chance that with a new battery it can be put back in working order .

 

[Tubetec]

After more precautionary checks I replaced the fuse and applied power to the HP3478A,
there was a few error messages initially at start up ,
About 45 minutes later its more or less stabilised and gives a good account of itself on the ohms range with a few different values of resistor,
I didnt bother bench marking it next to the Fluke with precission resistors yet , but all the indications are I have a fully functional meter
Ive only scratched the surface of what this unit is capable of but I must say its a pleasure to use ,

The only slight downer is the unit doesnt accept insulated bannana plugs so my favoutire probe leads wont fit unless I cut away the shroud .

I powered it off and back on and got the 'self test ok' message which is good sign.
A prolonged period powered up might be the best thing for these units .

 

[Tubetec]

I should re-label the thread , Four great pulls from the scrap heap ,

I lined up my 5 Fluke handheld meters and measured a cheap BNC 50 ohm terminator
all 4 of the 17x series meters flick between 51.1 and 52.2 ohms , the 187 measured 51.15 ohms ,
The 4378A measures 51.214 ohms ,


I had the unit on 24 hours already ,watching the measured values slowly perambulating up and down ,
I gave all the 4mm sockets a clean with a cotton bud and iso ,
I also lowered the contact resistance of the BNC adapter ,
This seems to have reduced most of the drift I was seeing , its still drifting very slowly downward , which can only be a good sign

Just aquainting myself with the 4378A user/technical manual and spec now ,
AC RMS voltage ranges have 100khz bandwidth and low noise ,
It also has a HPIB interface on the back , I see theres a modern HP/Agilent USB to IB adapter available on ebay for around 100 , seems to allow control via command promt from the pc as well as an interface for NI Labview etc .

A few people over on EEV blog figured out a way to backlight the 4378A LCD screen ,
brightens up a unit that dates back to 83 or 84 nicely ,


I have a question about the PSU's I was hoping someone could help me with ,
Both supplies are wired 110v , I have a 230 to 110V autoformer ,
it certainly works , but in the manual it does specifcally mention the unit needs 3 wire mains connection for correct opperation , is using an autoformer an issue in this case ,
The units are capable of 230volt opperation ,by changing out a couple of wire links on the transformer primary , so maybe thats the best option in this case .

I checked a little further into the Blackstar meter , found out it has a useful db range ,
the user interface isnt as nice as the HP , but it seems easy enough to calibrate to a known good standard , it should make a nice double check on the figures Im reading in REW .

 

[Gold]

I have an HP 400 that only works after it has been on for a couple of days. The electrolytic caps look like nothing else I've ever seen. Can they be replaced with normal high quality electrolytic caps?

 

[Gold]

About 10 years or so ago I along with others had to clean out my mmentor’s shop. There were piles of broken test equipment. Mostly HP. We couldn’t give it away. Most of it went in the dumpster. I kept a few pieces.

I don’t do much work with power amps but i have to work on a few coming up. I kept this General Radio 1840-A Output Power Meter because it’s a unique piece. I’m checking it out and will use it next week for the first time.

 

[RoadrunnerOZ]

I have a question about the PSU's I was hoping someone could help me with ,
Both supplies are wired 110v , I have a 230 to 110V autoformer ,
it certainly works , but in the manual it does specifcally mention the unit needs 3 wire mains connection for correct opperation , is using an autoformer an issue in this case ,
The units are capable of 230volt opperation ,by changing out a couple of wire links on the transformer primary , so maybe thats the best option in this case .

Mains ground is not part of the supply voltage reference looking at the schematics- so you can series or parallel multiple supplies of the same model to increase voltage or current respectively. Either the positive or negative rail can be grounded - if used this way the chassis obviously needs to be grounded via the 3 pin plug. The supplies can also be run floating. However you may get induced voltage in the chassis so it is probably a good idea to use the ground pin on a plug.
The 240/110 changeover mod just rewires the primary to either parallel the windings or series them but you do need to change the fuse value - it has no effect on grounding or not but your auto-transformer may not have a ground and you don’t want to connect the chassis to the Neutral line.