Turtlerock Forum

I have just spent the afternoon at a mates house having a look through his old allen and heath system 8 desk. It bit
the dust in a rather odd fashion on the weekend.

Symptoms:
- LED's light.
- No signal can be heard coming from anywhere... though the PFL meters jump marginally when PFL is engaged.
- Opened her up. Measure -15v to ground on the -15v bus wire. Measure nothing on the +15v bus wire.

Hmmmm. PSU issues?

- The 7915 measures -23v input (center pin) with -15.5v output (3rd pin).
- The 7815 measures 23v input (1st pin) but anywhere between 0v and 4v output (3rd pin).

Dead regulator?? If it is... it is a much calmer death than I suspected. No smoke. No bang. Not even a slightly tarnished fuse!

regulators certainly can just kark it without a song and dance , to dont assume you need a firestorm or burnt marks or twisted plastic

nice to meet you on the weekend btw
pity you made me pay so much for all that old junk that doesnt work
i might just check the regulators and see if i come up a winner:)

Sounds to me like you've tracked it down yourself already Dead 15V reg would certainly explain working leds but no sound.

I had a similar problem with my Ta@#$% tape machine earlier in the year. The machine was firing up but the transport controls weren't lighting up (or working). Turns out it was the 7805 (+5V reg)... 15V on the in, nothing on the out. There was no fireworks or burning electronics smell... just the transport not working.

Crack out the iron and replace that reg... I reckon you'll be in business!

Speaking of tape machines and ABC auctions... turns out the Studer B-67 I bought on saturday fired up, capstan spins... lights work. Haven't got any 1/4" tape to test but it's looking good so far. Not bad for 5 bucks I suppose!

It was nice meeting you too, Rick! It really is depressing knowing that the only thing I achieved at my first auction
was making you pay more. I'll know better next time Have you had a chance to fire up those big brown boxes?

Sorry I had to scoot prior to meeting you, Nick. Rick mentioned you were about but I was keen to hide under some bed covers in the
fetal position somewhere. What an intense experience! $5 for a B67? How can you go wrong?! I missed the start of the auction but
a chap mentioned that a bunch of reel to reels went for next to nothing. Do you know how much the Shure SM7's went for?

Regulator it is. Thank jeebus for that. All of the bus wires are threaded through the channel pcb's. It would be a major PITA to do work beyond the PSU. It is probably time for a PSU recap too.

The SM7's went for between 200 and 275 each ish. Peat on this forum actually bought 4 of them, crazy bastard. I think I might ask him for a job... seems like hes got money.

Sammas wrote:It was nice meeting you too, Rick! It really is depressing knowing that the only thing I achieved at my first auction
was making you pay more. I'll know better next time Have you had a chance to fire up those big brown boxes?

oh look if it wasnt you it was some one else thats how it flies
i am flat busted broke building the new studios , that was the only bit of fun i have had in a couple of weeks but i had to come over and say hello and explain what was happening in the nicest possible way because you guys were giving me the newbie at the auctions "glare' "
as in " you bought my thing you bastard" ....

after 9 long hours last night 7pm-4am ( with the help of some previously waylaid lexicon spareparts ) i repaired recapped and restored the 224xl reverb to its former glory, it looks and sounds amazing tonight , but frankly it was cactus ...a real basket case of issues
i reckon most people would have chucked it out ( well the abc certainly did)
so just as well i know what i am doing (err kinda) and i bought it for lunch money or it would have been a real mistake
thats the risk you take and you have to calculate the worst case senerio in those auctions , ie assume its broken and know where to go for spare parts at the right price


the akg bx20 reverbs will get a run though tommorrow they are sure to be dead but i reckon i will get at least one back and up and springing by the end of the week
or maybe they will never work again and end up as spare parts for my next attempt at looking clever
either way , it would have been better to get them for $5 each... bastard ! :0
but you cant have everything , i've tried

At least when you were bidding you two didn't know who the other was... All my prices got driven up by one of the guys that I gave a lift there. who's the stupid one here? That'd be me.

sorry saw my answer in above posts.

Check also any bypass capacitors around the 7815 regulator. Tantalum capacitors have a tendency to go S/C and the 7815 will self protect, but not actually die. ***Remove Power First***, Check with a multimeter on Ohms setting for a short between +15V rail and Ground. Remove reg and check between Centre pin and output for short . Then check for short to gnd. You sometimes see a bulge in the side of the tantalum and sometimes some of the metal oozes out a split, looks like a tiny solder blob.
I replace a lot of tantalums on Studer Audio cards

Speaking of Studers, Rick, how much did the A80 go for at the ABC auction ? I was down at the Mill with Andy pulling the A810 to bits.

ah, good to know the BX20's were somewhat broken..i was going to go...but i cant afford a fridge sized reverb in my bedroom!!

FFS.

i didnt pay attention to the A80 but it was pretty beat up

$650 if memory serves...

Just a wry observation .. do you think the audio guys in the 50's and 60's were trawling the trading post looking for old recording gear from the 20's and 30's because "all this modern valve stuff is too sterile"?

OK .. back into my corner now

In the case of STAX / Motown and some of the other 'iconic' studios that were actually set up in the 60's I believe most of them either used whatever they could get their hands on and / or custom built equipment. I think early STAX records were done entirely on a couple of AMPEX mixers and a mono tape machine and it wasn't until after the 'pro's' from Atlantic (Wexler / Dowd) arrived and told them otherwise that they got an Audiotronics built for them.

Hey Nick, I've got Studer Parts and Manuals for B67 if you need any

Alastair Reynolds wrote:Hey Nick, I've got Studer Parts and Manuals for B67 if you need any

This is good news alistair! We'll talk soon. Where abouts in Sydney do you hide out?

rick wrote:

Sammas wrote:It was nice meeting you too, Rick! It really is depressing knowing that the only thing I achieved at my first auction
was making you pay more. I'll know better next time Have you had a chance to fire up those big brown boxes?

oh look if it wasnt you it was some one else thats how it flies
i am flat busted broke building the new studios , that was the only bit of fun i have had in a couple of weeks but i had to come over and say hello and explain what was happening in the nicest possible way because you guys were giving me the newbie at the auctions "glare' "
as in " you bought my thing you bastard" ....

after 9 long hours last night 7pm-4am ( with the help of some previously waylaid lexicon spareparts ) i repaired recapped and restored the 224xl reverb to its former glory, it looks and sounds amazing tonight , but frankly it was cactus ...a real basket case of issues
i reckon most people would have chucked it out ( well the abc certainly did)
so just as well i know what i am doing (err kinda) and i bought it for lunch money or it would have been a real mistake
thats the risk you take and you have to calculate the worst case senerio in those auctions , ie assume its broken and know where to go for spare parts at the right price


the akg bx20 reverbs will get a run though tommorrow they are sure to be dead but i reckon i will get at least one back and up and springing by the end of the week
or maybe they will never work again and end up as spare parts for my next attempt at looking clever
either way , it would have been better to get them for $5 each... bastard ! :0
but you cant have everything , i've tried

Bah! You confused the glance! It was a "this guy knows exactly what he is doing" glance.

Hopefully all the springs and their drivers are intact in those boxes. I'd assume from there they are salvageable.

Oh! And regulators replaced... running a smooth +/- 15v. The System 8 is back in business.

...and my mate bought me a few beers and a slice of pizza for my services. Smiles all round really.

Sammas wrote:Oh! And regulators replaced... running a smooth +/- 15v. The System 8 is back in business.

...and my mate bought me a few beers and a slice of pizza for my services. Smiles all round really.

Careful! Before you know it you'll be fixing all your mates mixing boards for beer and pizza!

What do you spend your money on? Payments in cash just result in pizza and beer anyway!

too true!