Hello, and advice needed

[Weez]

Hello all,

First, happy holidays to everyone, hope 2012 was good to you.

I'm in the process of researching to outfit a basic bench setup for working on effects and amps, etc. I've done some searching on this and other forums, google, you name it, and I've gotten some good info. The first thing I'm looking to get is a decent scope, and I'd like to get a Tek 465 (since they seem to be so revered). However, after checking craigslist and the 'bay, they're all close to 400 bucks shipped. That seems a little crazy when Tek is selling their brand new digital scopes starting at 500... I may pick up a BK unit (model 1476, 10 Mhz, I believe...very basic) which will run around 150 shipped, but I'm not finished researching that. Anyway, regardless of the brand, most of the listings I'm interested in are from sellers who have no idea what the item is (only that it "powers up"), and don't come with probes. So...when I get a scope, what make/model probes should I buy?

In the interest of not buying something I'll need to replace, I could use some suggestions on the following stuff. I've researched just about all of this but,...what do you guys use? DIY, or just buy it? :

-variac (2 amps ok? or should I get a 4 amp unit)
-DC power (lots of options here)
-sine/square wave generator (I do have a line on a Heathkit unit)

Sorry for the wall-of-text first post, any input is greatly appreciated. Meantime, I'm off to scour the forums for more info.

Slainte,

Weez

[olddawg]

Those BK scopes were workhorses for TV shops got years. Make sure it triggers. They had problems sometimes. There are lots of good used scopes around. Leader comes to mind. Just don't buy a $100 scope and spend $200 on probes. Try to get a scope with probes. Preferably at least one 10:1. There are great signal generator phone apps out there for free. I have a big old HP 200 which looks and works great but it's pretty much a paper weight anymore. Most techs use an old reliable stereo with speaker load switches to drive amplifies under test with the tape out or take a pre-out level signal in the tape in. (Or Aux) you probably want a variac, preferably one with voltage and current meters. And a decent load bank.

[soundguruman]

Hello all,

First, happy holidays to everyone, hope 2012 was good to you.

I'm in the process of researching to outfit a basic bench setup for working on effects and amps, etc. I've done some searching on this and other forums, google, you name it, and I've gotten some good info. The first thing I'm looking to get is a decent scope, and I'd like to get a Tek 465 (since they seem to be so revered). However, after checking craigslist and the 'bay, they're all close to 400 bucks shipped. That seems a little crazy when Tek is selling their brand new digital scopes starting at 500... I may pick up a BK unit (model 1476, 10 Mhz, I believe...very basic) which will run around 150 shipped, but I'm not finished researching that. Anyway, regardless of the brand, most of the listings I'm interested in are from sellers who have no idea what the item is (only that it "powers up"), and don't come with probes. So...when I get a scope, what make/model probes should I buy?

In the interest of not buying something I'll need to replace, I could use some suggestions on the following stuff. I've researched just about all of this but,...what do you guys use? DIY, or just buy it? :

-variac (2 amps ok? or should I get a 4 amp unit)
-DC power (lots of options here)
-sine/square wave generator (I do have a line on a Heathkit unit)

Sorry for the wall-of-text first post, any input is greatly appreciated. Meantime, I'm off to scour the forums for more info.

Slainte,

Weez

get the 465, digital scopes bite.
10 amp variac
300 watt load resistors...

[Weez]

Thanks for the replies. I may end up going with a Tek, but my research is ongoing (I'm OCD about researching expensive tools - I much prefer to buy them only once).

I haven't seen any 10 amp variacs in my searches, could be I'm overlooking them, but most are of the 2 and 4 amp ones, and the 4's aren't as plentiful. There were only a couple General Radio 150v/5a units listed, so for starters I may grab one of those. If their current price is any indication, I should be able to upgrade later on and get most of my money back out of it.

I'm probably going to just build the dummy loads myself; they're pretty simple beasts and I can start with a 16 ohm unit which will cover almost any amp, and add 2 4 and 8 ohms with varying wattages later. The ones I've seen on the bay are large clumsy-looking jobbers from Hong Kong and China. I'm not looking to attenuate for lower-volume playing, just soak the power for maintenance and testing. I'm currently building an iso-cab so I can crank my Mesa, like it was meant to be played

Again, thanks for your input, I appreciate it.

Edit: I almost forgot...regarding the scope; am I correct in thinking that if the scope has a 10x feature built in, it's not needed as a feature on the probe?

[soundguruman]

Yeah, I just bought some 300 watt edge wound resistors, and mounted them in a Hammond cabinet, with banana jacks...
I used stove wire to hook 'em up. Easily takes double the rated wattage, without even breaking a sweat. Handy for testing SVTs and power amps!
I tapped the resistors for 8 and 4 ohm connections.
The Tek scope is what you really want. Best workhorse scope ever made...
The funny thing being, the $400 scope you bought on ebay originally cost the government, like $17 grand. That is no joke, I checked with the factory myself. There are so many old ones now, that you can find a working one for $200! A bargain, I would wager. And the 465 IS entirely handmade / hand stuffed / PtoP wiring on the controls.
Be sure to get the 465 service manual. The full one, not a xerox copy.
The variac, there are 8 amp ones from China... but of course if you find a Staco variac, etc... made in USA, you are far better off. There are lots of these from theaters, who convert to solid state dimmers. A lot of them (unfortunately) are being thrown in the trash / scrap metal. They ARE a treasure, and can be easily repaired or rebuilt with new brushes. So, keep a look out for the good one! You could always stack two together...
There is nothing better than a USA variac!
What you find generally, is that old equipment is better than anything new, offered these days. The old one is built way better, and was made to be repaired over and over again..

Thanks for the replies. I may end up going with a Tek, but my research is ongoing (I'm OCD about researching expensive tools - I much prefer to buy them only once).

I haven't seen any 10 amp variacs in my searches, could be I'm overlooking them, but most are of the 2 and 4 amp ones, and the 4's aren't as plentiful. There were only a couple General Radio 150v/5a units listed, so for starters I may grab one of those. If their current price is any indication, I should be able to upgrade later on and get most of my money back out of it.

I'm probably going to just build the dummy loads myself; they're pretty simple beasts and I can start with a 16 ohm unit which will cover almost any amp, and add 2 4 and 8 ohms with varying wattages later. The ones I've seen on the bay are large clumsy-looking jobbers from Hong Kong and China. I'm not looking to attenuate for lower-volume playing, just soak the power for maintenance and testing. I'm currently building an iso-cab so I can crank my Mesa, like it was meant to be played

Again, thanks for your input, I appreciate it.

Edit: I almost forgot...regarding the scope; am I correct in thinking that if the scope has a 10x feature built in, it's not needed as a feature on the probe?

[Weez]

Ok, just pulled the trigger on a Tek 475; ~245 bucks, shipped. Description said it was in good condition, photo showed a signal being measured (though that doesn't necessarily mean anything, I know). So now I need probes...couple of after-market, not-so-pricey ones should be ok, as long as they're rated for the scope (200Mhz), right?


In the event the scope has some issues, can anyone recommend a good repair service (I've read that Tektronix doesn't offer service for these and other out-of-production units)? The seller offers a 14 day return period, but it's pretty much only for DOA issues, and besides, when dealing with these old units on the 'bay one could play the return game indefinitely, racking up shipping costs the whole time. I will be tracking down a service manual, too (thanks Soundguruman).

[soundguruman]

Ok, just pulled the trigger on a Tek 475; ~245 bucks, shipped. Description said it was in good condition, photo showed a signal being measured (though that doesn't necessarily mean anything, I know). So now I need probes...couple of after-market, not-so-pricey ones should be ok, as long as they're rated for the scope (200Mhz), right?


In the event the scope has some issues, can anyone recommend a good repair service (I've read that Tektronix doesn't offer service for these and other out-of-production units)? The seller offers a 14 day return period, but it's pretty much only for DOA issues, and besides, when dealing with these old units on the 'bay one could play the return game indefinitely, racking up shipping costs the whole time. I will be tracking down a service manual, too (thanks Soundguruman).

The aftermarket probes (200 mhz, from china) unscrew their own cables. and fail from the wire strain.....and it will drive you nuts.
There are tons of used tek probes on e bay, not expensive. I would have bought those instead of the Chinese ones.
The tek probe has a special (it's tweaked) BNC, unlike any other. The probe changes the indicator lights on the scope, when you switch from X1 to X10, on the probe. This way, there is no confusion about which scale you are using. So, that's why it's cool to have actual tek probes, other than the fact that they are just better probes, altogether.
The tek clamp-on mini current probe is ultra-cool.(it's really small for tiny wires) I mean, the bees knees dude. If you can score that probe, go for it. You will be styl'in.

[Weez]

Thanks man, I'll see what's available...I haven't bought any probes yet, wanted to get some input first. But I may have to get some cheapies to tide me over till I can afford the good ones....those things are pretty pricey.

[Enzo]

I have been scoping for decades, and really, I have always got preferctly fine use from the basic cheap scope probes you can buy anywhere. Places like MCM or someone sells them for $20-30. Yes, get the X10 probes. The switchable X1/X10 are fine, just donlt get the X1 only type. You can spend a ton on a probe, and yank the cable out of the BNC connector just as soon.

Worry about scope repair when you need it. Most scope repair starts with simply cleaning the controls.

Remember this is guitar amps we are working on, not NASA space probes. None of the circuits are demanding of test gear. You don;t need 0.000001% distortion audio generators or scopes with 350MHz bandwidth. Basic heathkit audio generators are fine, as are ubiquitous old HP 200 series oscillators.


I like to get the best stuff myself, but consider: If you are learning to play guitar, do you need to get a $10,000 Gibson? Or is a $400 Strat good enough to learn on? I;'d say so. FInd cheap basic gear, and consider upgraded replacement gear as you learn the limits of the basic stuff. By usi8ng basic old stuff, you will learn what things you need better, and what things are fine as they are. That way you won't spend a lot of extra money on really high grade features you just do not need.

Where are you located?

Drop me a PM if you care to. I have a few items that might help you.

[Weez]

Thanks for the reply Enzo (I'll be sending you a pm soon).

I received the scope a few days ago. I have to say, I was pleasantly surprised that it appears almost new. There are no dents, very few scratches or marks (most of which are where the front cover makes contact with the rim), and none of the dials or buttons are dirty, cracked, bent, or broken. They all move smoothly (or click positively) and there's no fading or wear on the writing. I really don't think there's a single mark on the faceplate at all. This unit was one of a lot (the seller had a total of ten) acquired from a military surplus, apparently. It's a 475, but there's a plate affixed to the back indicating that it's an OS-261 (US Army CERCOM). Above the voltage selector on the back, it says that it has mod options 4 and 7 (I know I read what those were during my research, but can't remember right now). The manual says you can pull a button out and reduce the bandwidth to 20 Mhz, but the actual button indicates you can choose 100 Mhz as well as 20 (there are two detents as you pull it out). Maybe that's one of the mods...

There's a soft, mesh-type screen covering the CRT. Barring any refurbishment it may have seen over the years, if I had to guess, I'd say it either saw very little/light use, or was extremely well cared for. Being former military myself (USMC), I think it's a safe bet that accountability would be high with such a pricey piece of equipment.

I don't have probes yet, but I can get a DC trace on both channels which responds to positioning like I'm assuming it should. I'll go through whichever "performance checks" in the manual I can do when I receive the probes, which probably won't be until after Jan. 1. All I have is a signal gen., but if I can get a sine and square wave trace, I'm thinking I can call it a "working unit".

It's a lot heavier than I expected it would be, but its heft and the feel of the controls lend credence to Tek's reputation of putting out quality products. Overall, I'm quite satisfied with the purchase, and providing it works, I'll consider it money well spent.