Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Mar Wed 20, 2019 6:24 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 65 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Wed 21, 2018 2:42 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
One of the CAD211FE amplifiers have the new Nichicon Gold Tune capacitors completely installed. If someone else decides to restore this similar amplifier, what you'll notice about the bridge rectifiers is that they have large solder terminals but with very small wire holes. Cary Audio attached four wires on some terminals which makes it difficult to undo just one. I took my drill and enlarged the wire holes so soldering the many wires doesn't require such a chore for future repairs.

...I also went on a beans and rice diet these past couple of weeks so I could buy myself a waveform generator!!! It should arrive early next week :)


Attachments:
Lelon1.jpg
Lelon1.jpg [ 237.44 KiB | Viewed 778 times ]
CapStand2.jpg
CapStand2.jpg [ 129.29 KiB | Viewed 778 times ]
CapSolder2.jpg
CapSolder2.jpg [ 146.76 KiB | Viewed 778 times ]
CapStand1.jpg
CapStand1.jpg [ 188.67 KiB | Viewed 778 times ]
File comment: Epoxy applied and with 1/4" clearance to the bottom cover of the amplifier.
Clearance1.jpg
Clearance1.jpg [ 189.14 KiB | Viewed 769 times ]
File comment: One CAD211FE amplifier finished.
NichiconGoldTune.jpg
NichiconGoldTune.jpg [ 197.42 KiB | Viewed 768 times ]


Last edited by Smoky on Jan Thu 03, 2019 9:37 pm, edited 6 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Fri 23, 2018 9:01 pm 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
The #1 thing I have noticed about changing out the capacitors is that the oscilloscope does not have wild swings in voltage or frequency.

I attached the TDS420 and Bose speaker to the CAD211FE amplifier that has all of the capacitors changed-out except for the Cardas and Solen capacitors in the front end.

It is registering 500 micro-volts. It varies 20 micro-volts either way on the scope (480-520).

I've heard this said before "this amplifier will play only as good as the tubes you put in it."


Attachments:
TheTest1.jpg
TheTest1.jpg [ 196.51 KiB | Viewed 764 times ]
Final1.jpg
Final1.jpg [ 99.09 KiB | Viewed 764 times ]


Last edited by Smoky on Dec Sun 09, 2018 9:03 pm, edited 1 time in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Mon 26, 2018 1:47 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
I finished up the 2nd CAD211FE this afternoon and turned the lights down low for the test :)

I boot-up the Tektronix oscilloscope.

I plug in the amplifier.

After 20 minutes, I run SPC on the scope and then hook up the probe.

The second amp averaged 440 microvolts of noise floor!

The frequency on both amps show this similar noise level at a steady 60 Hertz.

Is now be the best time to try a power filter or conditioner to plug the amps into?

Anyway, this has become such an incredible experience!

Tomorrow night it's back to the SixPacs. More parts came in :)

...and my new piece of test gear was in a box at my door too!
A Siglent SDG1032X. It didn't come with any cables so I ordered up some 50 ohm BNC to RCA and BNC to BNC lengths.

I also remember that I started the rebuilding of the CAD211 amplifiers with a new 10' roll of Soder-Wick. I have only 3" left!


Attachments:
UnderTheStars.jpg
UnderTheStars.jpg [ 135.12 KiB | Viewed 749 times ]
FinalTest2.jpg
FinalTest2.jpg [ 103.84 KiB | Viewed 749 times ]
SDG1032X.jpg
SDG1032X.jpg [ 175.5 KiB | Viewed 748 times ]
SoderWick.jpg
SoderWick.jpg [ 113.85 KiB | Viewed 747 times ]


Last edited by Smoky on Jan Tue 01, 2019 4:11 am, edited 5 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Tue 27, 2018 12:14 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
On to my Mini-Me rendition of Mr.Carlson's Lab "Two Six Pac's on the Bench."


Attachments:
SixPacsOnTheBench.jpg
SixPacsOnTheBench.jpg [ 229.01 KiB | Viewed 743 times ]
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Tue 27, 2018 12:23 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
In an earlier post, I set up one Six Pac amp to discover it suffers from the same illnesses that Paul Carlson found in his amplifiers. An average of 7 millivolts of noise and hum is detected on the oscilloscope.

In advance, I purchased all new capacitors, a few octal sockets, and some 18g 1000v Teflon wire (UL1180). Great deals on Ebay can be found for the M16878/5 type wire in short lengths.

The first thing I'm going to do is relocate the high voltage reactor and suspend it off of the side of the chassis on standoffs. I purchased 1-1/4" #6 steel standoffs. Paul discovered that almost 4 millivolts of noise was eliminated just by doing so. To add more rigidity to the mount, I welded washers to each end to reduce flex.


Attachments:
Standoffs.jpg
Standoffs.jpg [ 133.6 KiB | Viewed 741 times ]
Wire1-1.jpg
Wire1-1.jpg [ 162.04 KiB | Viewed 620 times ]


Last edited by Smoky on Dec Mon 10, 2018 1:41 am, edited 4 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Tue 27, 2018 1:18 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
I'll be going step by step through each amp one at a time. Tonight I've got the guts exposed on one amp and I'm going to check the main filter capacitors with the ESR meter.

Looking at the numbers, and since these capacitors are in series, I'm guessing they're in pretty good shape.

Like I said before, the previous owner must have gotten nauseous of listening to all of the noise and hum :)

I'm replacing a couple of the octal sockets because they're cracked and chipped. Maybe it's because he kept changing-out tubes so often in an attempt to get rid of the noise!


Attachments:
ESR1.jpg
ESR1.jpg [ 168.41 KiB | Viewed 739 times ]
ESR2.jpg
ESR2.jpg [ 152.06 KiB | Viewed 739 times ]


Last edited by Smoky on Jan Tue 01, 2019 3:00 am, edited 4 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Nov Tue 27, 2018 1:47 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
To jump forward a little bit, Paul Carlson found that the high voltage filter reactor was making noise also due to "ringing."

He found that it was caused due to a lack of capacitance on the high voltage line going into the reactor.

He found that a .47uf capacitor, brought to ground after the diodes, fixed the ringing problem in the transformer. He used four 630v .47uf capacitors (two in parallel and in series) raising the voltage capacity to 1260.

I veered off course a little here because that combination looked a little crowded. Mind you, I have very little knowledge of electronics, but it's gaining momentum :)

I scoured Digi-Key and found these Kemet .47uf 1200v capacitors. They are of the 5% variety with a lifespan of 30,000 hours and made for DC filtering. They are large (1"x 2") but they will still fit nicely against the side of the chassis next to the diodes. One capacitor per amp, easy-peasy :)


Attachments:
Kemet.jpg
Kemet.jpg [ 158.91 KiB | Viewed 738 times ]
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Wed 05, 2018 2:27 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
So I'm back under the hood of the Six Pacs :)

I'm looking close into one of the amps and something pops out at me.

Look at pictures 1 and 2. Notice that the color bands on the screen grid to plate resistors are different! One bank of three EL34 tubes have one size of resistor and the other bank of three tubes have another!

Picture 3 shows one of the resistors has a burn hole in its starboard bow :shock:

Only one bank in both amps have 100 ohm resistors. The other three banks have 2K ohm resistors.

The tubes that I found installed in the amplifiers are Electro-Harmonix EL34EH.

From what information I could dig up on the internet, it is recommended that at least a 1K ohm screen grid to plate resistor be installed on each tube socket for this particular tube. I'm guessing that the 2K ohm size is fine but not so much the 100 ohm resistor?

So, say after me, "Digi-Key" :) ...wait a minute, that rhymes!

I begin to investigate further. I recall seeing a "tube fuse" holder on the back of the amp. Hmm, sign reads... 1/2 amp fast blow.

So any guesses what I find stuffed in it???

You betcha! A 250v AGC3!!!

And of course, Radio Shack is, coincidently I might add, flooding the market on deeply discounted fuses during my time of need :)

I'm on a mission to clean up this mess!


Attachments:
File comment: 100 ohm 2% on one bank.
ScreenGrid1.jpg
ScreenGrid1.jpg [ 186.72 KiB | Viewed 684 times ]
File comment: 2K ohm 5% on the other bank
ScreenGrid2.jpg
ScreenGrid2.jpg [ 172.82 KiB | Viewed 684 times ]
File comment: Holy fire at the fire station Batman!
ScreenGrid3.jpg
ScreenGrid3.jpg [ 163.54 KiB | Viewed 684 times ]
Holder1.jpg
Holder1.jpg [ 213.14 KiB | Viewed 683 times ]
Fuse1.jpg
Fuse1.jpg [ 136.52 KiB | Viewed 683 times ]


Last edited by Smoky on Dec Mon 10, 2018 3:34 am, edited 1 time in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Fri 07, 2018 8:08 pm 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
When Paul Carlson went searching for the cause of the buzz in the high voltage reactor, he used his Tektronix Type 547 oscilloscope to directly read from the incoming blue high voltage wire to the choke.

I was given a non-working Tektronix TDS420 a few months back that I repaired in another thread. Along with the oscilloscope, my neighbor gave me a Tektronix A622 AC/DC current probe. It is rated 600vdc, 600vac, and 1200vac peak.

The blue wire in the first picture is the high voltage supply to the reactor. I measured this wire for voltage while the amplifier was running with all tubes installed and a speaker attached to the output terminals. My Fluke 8024B measured 424vdc.

Do you think it is possible that this current probe is sensitive enough or even capable to detect "ringing" in the waveform while looped around the high voltage wire?

I desoldered the blue high voltage wire from the diodes since it was routed tight to the chassis. It is now soldered back into place but with enough space to allow the probe to hook around it.

**Update**

I hooked up the probe. I activated the "Zoom" feature on the oscilloscope to 20x.

I'm hoping that what I'm seeing at the bottom of the waveform is ringing?


Attachments:
HighVoltage1.jpg
HighVoltage1.jpg [ 178.64 KiB | Viewed 670 times ]
Probe1.jpg
Probe1.jpg [ 196.83 KiB | Viewed 670 times ]
ProbeAttached.jpg
ProbeAttached.jpg [ 155.02 KiB | Viewed 659 times ]
Ringing1.jpg
Ringing1.jpg [ 180.7 KiB | Viewed 651 times ]
Ringing2.jpg
Ringing2.jpg [ 186.46 KiB | Viewed 651 times ]
Ringing4.jpg
Ringing4.jpg [ 158.89 KiB | Viewed 651 times ]


Last edited by Smoky on Dec Sat 08, 2018 5:58 am, edited 13 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Fri 07, 2018 11:10 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5026
Location: Montvale NJ, 07645
Smoky wrote:
my neighbor gave me a Tektronix A622 AC/DC current probe. It is rated 600vdc, 600vac, and 1200vac peak.

You have nice neighbors. I am moving to Apex NC (right next to you) in a year or two. I purchased the property last year.


Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Sat 08, 2018 12:00 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
That's terrific!

I'm going to breakfast in Apex tomorrow. My friend lives near the Hwy 64W and 55N crossover.

The Old Jenks Road :)

...we practice our rifle marksmanship out of his garage window on rainy days!


Attachments:
File comment: Jon Wolfe LRB M1A with a Krieger Stainless Barrel
Rifle4.jpg
Rifle4.jpg [ 155.14 KiB | Viewed 663 times ]


Last edited by Smoky on Jan Thu 03, 2019 9:42 pm, edited 1 time in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Sat 08, 2018 2:00 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5026
Location: Montvale NJ, 07645
I like shooting too, and have spent 32 years as a carpenter though my formal education is in electronics, so we have a bit in common.
I am surprised that you can shoot over there (Jenks Rd) as it is getting pretty populated.
My property is 6 acres up off 751 right next to the lake. Many thousands of acres of State game land around the lake which I have direct access to. My neighbors there are all very cool and very staunch conservatives. I can't wait to get out of NJ.


Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Sun 09, 2018 5:32 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
Just be very mindful of the ticks.

A friend of mine contracted Lime disease a few years back from one.

...lots of small church barbeques around there too :)


**Back to the amplifiers**

One of the Six Pac amplifiers has been given a new lease on life with the installation of a .47uf 1000v 5% capacitor between the diodes and the high voltage choke. The buzz is down substantially and the noise floor plummeted to ~600 microvolts!

On the second Six Pac amplifier, I'm going to try the .68uf Epcos 1000v 5% capacitor to see if it knocks the buzz out completely without raising the B+ by too much.

Both amplifiers have evidence of previous part replacement and the soldering is terrible in those areas. One of the Jensen capacitor's leads was loose around a terminal tie strip!

The sockets sit too deep in the chassis to replace just one that is cracked. Instead, I screwed new Russian sockets, 50 year old new :), on a board at the same centerline spacing that is in the chassis. The socket "strips" drop right in prewired. Now I have only two or three wires to solder to finish the job inside of the chassis! This time I bought the Russian octal and 9 pin sockets that are not glazed on the top surface. They look so cool from above.

The small .10uf Solen capacitors that were mounted tight and inbetween the tube sockets didn't look too healthy either. They looked to be oozing glue or something so I replaced them with new. The newer Solens looked slightly different in shape but a whole lot happier :) I mounted them a little further away from the sockets!

The Nichicon axial capacitors were replaced with new long-life Rubycon radials to make room for the soon-to-be relocated choke.

Also, the mis-matched screen grid to plate resistors have been replaced by all-new Vishay Dale wirewounds.

I'm not going crazy with exotic caps and stuff like that. As a matter of fact, I'm spending just as much on shipping as I am on parts! The last electronic's store closed in Raleigh about 10 years ago. I'm just fixing stuff and replacing parts with solid and long-term performers.

Quality matched tubes is where I'll spend :)


Attachments:
ProbeSix.jpg
ProbeSix.jpg [ 169.03 KiB | Viewed 620 times ]
OMG.jpg
OMG.jpg [ 127.65 KiB | Viewed 620 times ]
Jensen1.jpg
Jensen1.jpg [ 194.77 KiB | Viewed 620 times ]
SocketStrips.jpg
SocketStrips.jpg [ 143.19 KiB | Viewed 620 times ]
Solen.jpg
Solen.jpg [ 126.59 KiB | Viewed 605 times ]
SocketStripInstall.jpg
SocketStripInstall.jpg [ 180.82 KiB | Viewed 605 times ]


Last edited by Smoky on Dec Tue 11, 2018 7:54 am, edited 4 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Tue 11, 2018 7:42 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
One of my best investments in tools so far has been this $2 Radio Shack heat sink. When soldering socket pins and terminal tie strips, it keeps you from wasting solder due to the metal overheating :)

Here's some of my newly-acquired old equipment. $40 each from Dale, a retired technician from Glaxo!


Attachments:
Sink1.jpg
Sink1.jpg [ 91.89 KiB | Viewed 605 times ]
File comment: Sencore SC61 Waveform Analyzer
SencoreSC61.jpg
SencoreSC61.jpg [ 210.5 KiB | Viewed 500 times ]
File comment: Sencore LC53 "Z" Meter pumping out 650 volts into a capacitor!
Zmeter.jpg
Zmeter.jpg [ 175.94 KiB | Viewed 500 times ]
File comment: The Six Pac amplifiers now idle at 1.75 amps. No more blowing of fuses :)
Tenma.jpg
Tenma.jpg [ 213.57 KiB | Viewed 419 times ]


Last edited by Smoky on Jan Thu 03, 2019 3:19 am, edited 4 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Dec Mon 31, 2018 12:32 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
So to bring things back up to speed, The Six Pac amplifiers need to have their high voltage chokes lifted from the chassis and relocated to reduce the interference with the output transformer.

I resorted to fashioning an aluminum bracket to place the choke 90° from standing and using a standoff to kick it another 45° to clear other components. I decided not to drill holes in the side of the chassis for standoffs. A thin plastic spacer cut from a sheet is sandwiched between the bracket and the metal chassis before it is screwed down. With the loosening of one nut, the choke swings up and out of the way for any future repairs. Rock solid!

Most of the soldering of the components was done on the bench. Much easier that way :)

One of the Six Pac amplifiers is 95% rebuilt and waiting for a final adjustment to the capacitor to reduce the "ringing" that causes the high voltage choke to buzz (The blue square mounted to the chassis near the diodes). The second amp is currently being disembowelled :)

All new Russian sockets, Rubycon and Solen capacitors, and matching resistors.

In the last picture, you can see a white jumper wire. I extended the terminal tie strip by one notch. The jumper is in between the IN5408 diode and the Rubycon 2200uf capacitor that supplies voltage to the 12BZ7. Right now the voltage hovers around 6.82 volts. If for some reason the voltage rises in the future, the jumper can be replaced with a resistor.


Attachments:
ChokeBracket.jpg
ChokeBracket.jpg [ 172.57 KiB | Viewed 500 times ]
TieStrip.jpg
TieStrip.jpg [ 178.35 KiB | Viewed 500 times ]
Bracket1.jpg
Bracket1.jpg [ 250.31 KiB | Viewed 499 times ]
Choke2.jpg
Choke2.jpg [ 228.74 KiB | Viewed 498 times ]
SixPacsRock1.jpg
SixPacsRock1.jpg [ 223.98 KiB | Viewed 498 times ]
SixPacsRock3.jpg
SixPacsRock3.jpg [ 249.96 KiB | Viewed 498 times ]
SixPacsRock5.jpg
SixPacsRock5.jpg [ 254.39 KiB | Viewed 496 times ]
Jumper.jpg
Jumper.jpg [ 231.49 KiB | Viewed 493 times ]


Last edited by Smoky on Jan Tue 01, 2019 5:21 pm, edited 4 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Jan Tue 01, 2019 3:14 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
With one Six Pac amplifier 95% rebuilt, and with the help of the Sencore SC61 Waveform Analyzer, I was able to detect the "ringing" that plagues these amplifiers from the factory!

I attached the probe to the wire between the diodes and the high voltage choke.

The ringing is clearly visible.

Note: if I widen the time base on the scope, the two small lines at the bottom of the waveform flutter up and down alternating to the DC pulses.

That spike in voltage that you see is 50 volts tall :shock:


Attachments:
Sencore2.jpg
Sencore2.jpg [ 71.89 KiB | Viewed 482 times ]
Ringing.jpg
Ringing.jpg [ 91.08 KiB | Viewed 481 times ]


Last edited by Smoky on Jan Tue 01, 2019 7:39 pm, edited 5 times in total.
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Jan Tue 01, 2019 3:35 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
My first attempt to clear up the "ringing" problem was to install a Kemet .47uf axial capacitor rated at 1200vdc.

One end of the capacitor is attached to the output of the diodes and the other is attached to the star ground.

The waveform smoothed out quite a bit but the high voltage choke still buzzes.

The peak-to-peak voltage rose by 1.


Attachments:
Sencore5.jpg
Sencore5.jpg [ 179.33 KiB | Viewed 481 times ]
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Jan Tue 01, 2019 3:41 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
In my second attempt, I installed a Epcos/TDK .68uf radial capacitor rated at 1000vdc.

The waveform smoothed out even more and the noise of the choke dropped by 80%.

The peak-to-peak voltage rose by 2.

Progress is being made and you can literally see it!

With more capacitors on their way from Digi-key, the next step up in capacitance will be .88uf and to 1.01uf if need be.

Expected delivery is Friday, so stay tuned :)

Happy New Year!!!


Attachments:
Sencore6.jpg
Sencore6.jpg [ 138.82 KiB | Viewed 480 times ]
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Jan Thu 03, 2019 2:56 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
Take a look at the wafeform now!

The bias setting from the owner's manual recommends 220ma to 230ma.

This is way too high!

Without adding any more capacitance, I rolled down the bias setting, the bottoming-out of the waveform disappeared (the flattening) and the buzzing from the choke stopped!!!

My milliamp meter reads 155.

I wrote down more notes and will disclose my findings when the new capacitors arrive and are tested.

I'm beginning to see an interesting trend unfold :)


Attachments:
OMGmoment.jpg
OMGmoment.jpg [ 122.54 KiB | Viewed 420 times ]
Top
 Profile  
 
 Post subject: Re: Cary Audio CAD211FE and AES Six Pac Amplifier Repairs
PostPosted: Jan Fri 04, 2019 3:38 am 
Member
User avatar

Joined: Aug Fri 17, 2018 5:33 pm
Posts: 135
Location: Raleigh, NC
Here are the before and current oscilloscope readings of the first Six Pac that has been rebuilt so far. A Bose speaker is attached and all tubes are installed and the amplifier is idling.

I notice noise on the waveform and I think it may be due to the new resistors. One amplifier had original resistors still in its hull and the amplifier I'm just finishing up was the one with a bunch of mismatched ones.

The EL84 and EL34 tube sockets are where I installed new wirewound screen grid resistors. The originals were metal oxide resistors. Would this change add noise?

Or could the noise be coming from the original electrolytic main filter capacitors? They are 15 years old and measure ~525uf and check out good on the Sencore Z meter at 400volts. Who knows?

All in all, the amplifier is doing much better :)


Attachments:
SixPacTest1.jpg
SixPacTest1.jpg [ 134.67 KiB | Viewed 395 times ]
Update2019a.jpg
Update2019a.jpg [ 247.72 KiB | Viewed 395 times ]


Last edited by Smoky on Jan Sun 06, 2019 7:00 am, edited 3 times in total.
Top
 Profile  
 
Post New Topic Post Reply  [ 65 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 6 guests



Search for:
Jump to:  


























Privacy Policy :: Powered by phpBB