After I replaced the capacitors and installed a polarized plug, I had no hum at all. The wiring in my 9301s did not take the center tap of the balance pot to ground, for some reason. Anyway, I have zero hum and I even used a scope to verify.
Console stereos: 1958-84
- Thread starter cfz2882
- Start date
phillymatt53
Well-known member
You've got me a bit confused there, I assume you are talking about the HUM balance pot.
You say that the balance pot wiper doesn't go to ground - THAT would be of course EITHER the HUM balance, AND the input level balance.
Regardless of whether there's hum or not, this is my answer....
The HUM balance pot wiper DOES go to a 100 ohm cathode bias resistor which IS grounded, and as I mentioned, keeps those cathodes and the filaments NEAR ground potential, which is what Magnavox did on purpose.
The reasoning, if you can understand it is - it's to prevent the input and output tubes from any "flashover" or arcing issues inside the tubes from happening, along with raising the filaments above ground potential for the 6EU7's.
A lot of people (mainly amateurs/hobbyists/internet guru's) don't fully understand this type of design or why it is a necessary thing to do with tube amplification.
Magnavox didn't just put it in there for looks.
I assure you I am not an amateur, but my background is in mobile communications, so I do assume you are correct. But, I love fiddling around with stuff just to see what would happen. Now if I could only find a blank chassis or a place near me that does sandblasting, I would remove all the parts and rebuild, I'd also replace all the passive components I could. Since both my 9301's came from less than clean environments, (barn and landfill) I'd like to get them all spiffed up like I've seen others do.
phillymatt53
Well-known member
"Spiffed up" is worth it if it's going to be a visable piece on display.
But if hidden inside the console, I wouldn't get obsessed with appearance other than some reasonable cleaning.
The 9304-20 that I pulled from a console in 2002 was in decent shape, just dusty.
I've done extensive modifications to it to bring it up to the best performance that it's capable of.
Normally, a pair of EL84's in push-pull can put out about 10 watts before clipping.
And the 6EU7's are configured in a simple Paraphase splitter design to feed those outputs.
But a more stable and balanced design with lower distortion is a cathodyne phase splitter, AKA Split-Load Inverter, which was my choice.
In addition, the original output transformers have their frequency limits too, and I replaced them with the Dynaco Z565 outputs, which are of a "Ultralinear" design and a wider more accurate frequency response.
On top of those mods, I went for the Dave Gillespie modification of biasing the outputs from the original cathode bias to Fixed Bias controlled by a regulator.
The result of all this is substantialy higher power (17 watts/channel), with much less chance of distortion at higher volume peaks/levels, Superior frequency range, and increased tube life.
That amp now can drive my power-hungry Advent Maestro floor speakers to window-rattling levels with clean audio and solid bass that gives me goosebumps, and crystal clear highs.
I housed it in my own custom case
Some pics...
Damn! You do good work! That component is beyond beautiful. Mine is in the console, but the problem is that I know it is in there, not being as pristine as it could. Thanks for all your help and info. I once had the skill to create something like this, but that was way back during Disco.
phillymatt53
Well-known member
Thanks Eugene.
I'm like an old, experienced Surgeon, and insist on performing my work to extremely high standards - mostly.
Being in the electronics repair business has given me this blessing.
Plus, I'm picky about doing things the best way, no shortcuts, no slop.
A lot of tediousness is involved, which doesn't much bother me, hell, it kills time and keeps me off the streets. LOL!
You are correct, cfz. I just sent the Magnavox/Collaro turntable in to Vintage Record and Turntable Repair for a complete rebuild. I'm good with the electronics part, but for the electromechanical part, I have no skill.
phillymatt53
Well-known member
Good luck with that Collaro Eugene, those Collaro's are quite complex to overhaul. - I should know.
Some adjustments even require a feeler gauge in order to set a specific adjustment for tonearm control and cycling.
But when they're properly done, they'll go for decades without an issue.
Yes, they have about two gillion adjustments that can be set incorrectly even if one follows the instruction manual. The good news is, that if all the adjustments are done correctly, if needed, the changer will be stable for decades, assuming all the other parts are in good order.
phillymatt53
Well-known member
Instruction manuals are not the same as Service Manuals.
I've got a Magnavox Service Manual library 3-ring book 3 inches thick with the amps, tuners, consoles, and the Collaro record changers dated 1959 to 1963.
It's been a blessing when I needed it.
It even has early transistor radio service data.
I may have misspoken. I have a similar 3-ring book as well. It has the 600 series Collaro changers Service Manual in it and is dated 1963. When I took one look at the blow-up diagrams in it, I knew that fiddle-farting around with it was not for me.
Collaro made record changers until 1992, later than BSR.
phillymatt53
Well-known member
Is that so?
I find that hard to believe, so please post some information of that, thanks.
cfz2882
Well-known member
Newest Collaro I have seen was from about 1978-had pot metal motor housing instead of black stamped steel of earlier ones
phillymatt53
Well-known member
Yes, the quality of Collaro's went downhill towards the end.
By 1980, record changers were history, single-play turntables were the only ones left, until the late 1980s when CD's took over the industry.
Panasonic-Technics made a couple of "stacking" models in the 70's that were quite respectable machines.
I serviced a 1980 Zenith console stereo (with 8-track!) for my neighbor a while back.
It had the last BSR changer in it, a cheap model which was likely leftover stock that was part of the liquidation that both BSR and VM had to clean out when they ended their corporations.
On another note, in the early 1990s, the chinese imported crap using the "Crosley" brand name attempted to revive the changer in some of its lousy phono products.
They called it the "Stack-O-Matic", which was a flimsy plastic hunk of garbage based on a cheap BSR design.
I got one in the shop for repairs once, and man oh man, I had to laugh at the pathetic attempt that they tried to sell people.
Today, the only stacking machines that I'd ever play my good records on are a few Garrard models or the Dual German changers.
I've got a few vintage records in mint condition that are coveted and worth a lot since they are "original" pressings.
The Patsy Cline double album on Decca records that came out in 1963 right after she was killed - "The Patsy Cline Story"
And "Dark Side Of The Moon" by Pink FLoyd.
Among some other classic hard-to-find albums.
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VM was done in 1977. BSR went out in the mid-1980s. I remember reading that Collaro continued to 1992, but perhaps I'm mistaken. The last Collaro turntables may not have been masterpieces, but they're still better machines than 1970s BSR's, in my opinion. The last VM changers weren't so hot either.
I've never been unlucky enough to have a Stock-O-Matic cross my workbench.
I've never been unlucky enough to have a Stock-O-Matic cross my workbench.
phillymatt53
Well-known member
If you read something from the internet about Collaro's, ending of manufacturing, it's likely misinformation.
phillymatt53 wrote:
"The record changers used in them ceased to be manufactured by 1977, when the last company, VM, Voice Of Music, closed down.
BSR itself went out of business around the same time."
More misinformation. V-M was not the last man standing. If Collaro wasn't, BSR was.
"The record changers used in them ceased to be manufactured by 1977, when the last company, VM, Voice Of Music, closed down.
BSR itself went out of business around the same time."
More misinformation. V-M was not the last man standing. If Collaro wasn't, BSR was.
phillymatt53
Well-known member
So, you're going to "nitpick" about specific actual dates?
I'm really not that anal to be bothered with trivial history things like that.
If you consider 8 years to be trivial, so be it.
BSR ran V-M out of business. BSR did not go out of business, they stopped making turntables.
BSR ran V-M out of business. BSR did not go out of business, they stopped making turntables.
vacerator
Well-known member
I know that Sony all in one table and cart type systems had BSR turntables beyond 1980 because my friend bought one new.
cfz2882
Well-known member
BSR continued at least into the mid 1980s,but the proper "made in England" AC motor ones were done by then: I have a 1985 sears combo stereo and it has a "BSR",totally "BPC", Taiwan made DC motor belt drive turntable-even has the red label underneath like the old British ones.
The stacking Dual 1006 is my favorite changer of all time. It was even more Rube Goldberg-ish than a Collaro. I don't think there are any left, however.
phillymatt53
Well-known member
I sold a pristine Dual 1009F with a new Pickering/Stanton cartridge a few years ago on Craigs List, fully serviced by me.
Excellent machine, which blows away today's plastic "high end" garbage.
And I've got a Dual 1019 just serviced, sitting on the shelf, base and dustcover, all the spindles, and a new Audio Technica cartridge on it, which will eventually be listed on CL too.
That machine will go for a sweet price of course!
But worth every penny.
Here's the 1009F sold...
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rinso wrote: "The stacking Dual 1006 is my favorite changer of all time. It was even more Rube Goldberg-ish than a Collaro. I don't think there are any left, however."
The Dual 1006 series is just off the wall.
The Dual 1006 series is just off the wall.
phillymatt53
Well-known member
Jesus! - in all the decades of servicing countless record changers, I never had a 1006 in the shop.
That's just NUTS!
phillymatt53
Well-known member
Here's the kind of Dual's that I'm experienced on....
vacerator
Well-known member
My father in-law had a Dual. I don't know what model but it was from the later 70s. or early 80s. His first was a Philips with outlined lighted round buttons. Around 1998, he gave us all his lps and was more into CDs. No one knows what happened to the Dual. Probably donated to Goodwill.
phillymatt53
Well-known member
Those Philips, the ones with the lighted buttons, were troubleprone machines.
The lightbulbs inside the buttons would burn out, and then the button would not work.
See, the bulb was used as a to trigger a sensing "eye" system.
As for the vintage Duals, they're considered like GOLD these days, and worth much more than when they were new.
Heck, I sold that 1009F for $350 and the new owner loves it.
The 1019 I have will likely be around $475-550 when I list it.
I owned a top model 1229 that cost me $200 back in 1974, plus the walnut base and dustcover cost another $60.
Plus a Shure top line V15 Type 2 Improved eliptical cartridge that cost $68, and the 45 RPM stack spindle adapter for $8.50
Add that up - total investment with tax, of $353.32 in 1974 dollars.
And I was only 21 at the time, struggling with two jobs and living at home.
I've always loved music, and just had to hear it with the best equipment.
I also had a Panasonic 'high end' receiver, Panasonic cassette deck, and the famous Advent "smaller" speakers, along with Koss Pro4AA headphones.
Oh, and also a Sony reel-to-reel that alone cost me $400.
That system lasted me right up to 1982.... when my first apartment got broken into and everything was stolen.
vacerator
Well-known member
Matt that's probably why dad got a Dual. It had a wooden base and was a single play automatic. My first cartridge on my B.I.C. 940 was a Sure V15 elliptical. I sold the BIC and got my Technics SL 220 with a Pickering V 4 II hyper elliptical. Still have both. I've taken a liking to my newest Ortofon 2M blue.
