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Starting the 300B Laurel's again


Glensing
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Yes, newbie but lurked here many years. So covid-19 helped get me serious with my HIFI hobby again. I just finished restoring my 1983 WO black grill Belle's and can't think of a better reason to get my Welbourne Labs Laurels (factory built) out of storage (15 years). My variac will arrive in a day or two to bring them back up but I am wondering, if it will be ok to just start them? I know nothing about these designs or where to check voltages so I'm thinking I should find a knowledgeable SET person around here to go through them for me. Might be some upgrades needed as these are not the ultimate version.  I would love to hear thoughts and ideas.

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It probably is a good idea to recap it, at least the big power supply ones, before firing it up but bringing the voltage up with the variac is an alternative. What you hope happens with the variac is the old caps reform. Look at the caps to see if there is anything leaking out of them is a good place to start. Chances are it will play just fine as is if there is no cap leaking. 

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Henry is correct, have a look at the caps no leakage and no swelling, bring them up slowly on the variac .  I have a couple amps at least that old with no issues (though they have not sat in storage for 15 years)  I did find a NOS dynaco st70 MK2 some time ago that sat in storage for 30 years it played fine with no issues I also had a TT that was 35 years old NOS that played fine with no issues,

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Thank you gentlemen...that gives me the confidence I needed. I recapped the Belle's CO networks with Crites Sonicaps so this leads me to think I can get the Laurels running myself. Is there any reason to think there may be better main caps than what Ron used? If so is it reason enough to do it and will it make a sonic difference? Gonna go find my head lamp cause the variac is out for delivery. Woohoo Thanks again

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20 hours ago, Glensing said:

Thank you gentlemen...that gives me the confidence I needed. I recapped the Belle's CO networks with Crites Sonicaps so this leads me to think I can get the Laurels running myself. Is there any reason to think there may be better main caps than what Ron used? If so is it reason enough to do it and will it make a sonic difference? Gonna go find my head lamp cause the variac is out for delivery. Woohoo Thanks again

 

If you liked the way the Laurels sounded just use the same caps. Replace all of them to avoid future problems.

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Got ahead of myself there for sure Jeff. Thanks.

So While starting the Laurels, the rectifier started acting up at just above 65 volts. I took it to 50 volts over 10 min left it there for 30 min. As I increased the voltage to maybe 65 the variac buzzed from the rectifier shorting  (a little light show) and I shut it down. Darn it.

So I ordered the Sovtek 5AR4's. Should I give it another go when I get the tubes?

The twins look good under the hood. I'll try to insert.

300B bottom.jpg

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Thanks Maynard...I am in Arkansas. My first thought was to find a tech to get them back in my system. After a no luck novice effort looking (driving distant shops) I thought I could handle bringing them up with the variac. Otherwise I have extensive packaging experience and our company can help with freight rates. 

Any recommendations are needed ?  (maybe a tube amp designer). 

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Before you consider shipping search for any ham or antique radio clubs in your area.  Both often have members who are audiophiles, many of whom are very well trained in tube electronics.  This is a very easy repair so it would be a shame to incur significant shipping costs and risk damage to the amp.

 

 

Maynard

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  • 1 month later...
On 11/22/2020 at 4:55 PM, Glensing said:

Thanks Maynard...I am in Arkansas. My first thought was to find a tech to get them back in my system. After a no luck novice effort looking (driving distant shops) I thought I could handle bringing them up with the variac. Otherwise I have extensive packaging experience and our company can help with freight rates. 

Any recommendations are needed ?  (maybe a tube amp designer). 

 

Where are you in Arkansas?

 

I see one big cap and two small elextrolytics...

 

 

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15 hours ago, seti said:

Where are you in Arkansas?

I'm in Fort Smith.

I should be getting the PS electrolytic caps any day now. Its either recap myself or wait till spring (Not). 

If I'm going to drive with tubes, I must know them (think). Been a busy 2 weeks for sure.

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5 hours ago, Glensing said:

I'm in Fort Smith.

I should be getting the PS electrolytic caps any day now. Its either recap myself or wait till spring (Not). 

If I'm going to drive with tubes, I must know them (think). Been a busy 2 weeks for sure.

 

 

Ahh bummer. I'm in little rock.

 

 

 

 

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  • 2 weeks later...

Happy to have a look Glen.

 

Your Laurel's were built more neatly than many other Welborne kits I've seen or worked on.  It will be a very simple problem to remedy.  It may also be surprising to learn that the power supply electrolytics, as well as those in the 300B filament supply, may be perfectly fine.  Truly.  If you have hum, we'll see whether it's 120cps or 60, and that can help diagnose the problem.  There is NOTHING that can't be repaired on these things, Glen.  Moreover, they are actually very simple, and in my opinion, extremely good sounding amps.  I've built my own 300B amplifiers using a different schematic/design, and, after fixing another pair of Laurel IIs, have decided to rebuild my own using the Laurel II schematic.  Ron Welborne also worked with another designer by the name of Pete Millett, who is an extremely talented designer.  And of course Jack Eliano from Electra-Print.  Eliano was the one behind the Direct Reactance Drive triode amps. Anyway.

 

I sent you a PM

 

erik

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Well I went for it. My plan was to replace caps with like caps. The Solen's were available and that was about it. It took me 2 weeks to decide what electrolytic caps to purchase. I was most nervous about the dual 47uf 500v to replace the elna ceriafine, because of all the stuff I read about the sound of caps at this location. I ended up getting from Just Radios the  "47uf + 47uf at 500 Volts RG Can Ecap with solder lugs" that fit my original clamp. Next issue I had was the radial Xicon 100uf 250v at the 5ar4 and ended up going with an axial Vishay. I did replace 1 electrolytic on the MU stage and that was an Elna Silmic II 100uf 50v for the Elna Cerafine at the 6sl7. 

Do you all remember the first time you stuck an iron in a chassis. WOW  Anyway I put the RME ADI-2 DAC into the first with a Belle and it started playing music at 85 volts, same with the other. So Happy. It's now getting late so I put them on line voltage streaming overnight, just loud enough to hear them from the bedroom. 

The next morning I put on Brothers in Arms for a sound session and mediately flattened out the EQ on the RME as I no longer needed to cut the HF any more. I don't remember 15 years ago feeling so euphorically pleased from what I was hearing. No hum whatsoever. It's a great day.

Thanks to all.

 

Glen

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On 1/6/2021 at 12:06 PM, Glensing said:

Well I went for it. My plan was to replace caps with like caps. The Solen's were available and that was about it. It took me 2 weeks to decide what electrolytic caps to purchase. I was most nervous about the dual 47uf 500v to replace the elna ceriafine, because of all the stuff I read about the sound of caps at this location. I ended up getting from Just Radios the  "47uf + 47uf at 500 Volts RG Can Ecap with solder lugs" that fit my original clamp. Next issue I had was the radial Xicon 100uf 250v at the 5ar4 and ended up going with an axial Vishay. I did replace 1 electrolytic on the MU stage and that was an Elna Silmic II 100uf 50v for the Elna Cerafine at the 6sl7. 

Do you all remember the first time you stuck an iron in a chassis. WOW  Anyway I put the RME ADI-2 DAC into the first with a Belle and it started playing music at 85 volts, same with the other. So Happy. It's now getting late so I put them on line voltage streaming overnight, just loud enough to hear them from the bedroom. 

The next morning I put on Brothers in Arms for a sound session and mediately flattened out the EQ on the RME as I no longer needed to cut the HF any more. I don't remember 15 years ago feeling so euphorically pleased from what I was hearing. No hum whatsoever. It's a great day.

Thanks to all.

 

Glen

 

 

Great job!!!! It is addictive. You might as well do a bottlehead kit 8-)

 

 

 

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Great job!!!! It is addictive. You might as well do a bottlehead kit 8-)

 

 

Thanks Seti... Rewarding yes, addictive, not yet. I think my nerves are still frayed a bit. I'm afraid I would be the Bottlehead. But I do have some general use (bought the wrong ones) capacitors in stock now (humm).

I really thought I would still need help with the bias and such but they are so fun to listen to, I'm just going to keep them where they are for now.

 

The best discovery with  my SE system so far, is listening at low volume  I never thought I would ever say that. The worst part is, I now know what they mean by poor recordings.

 

Now I need a preamp so I can spin some Vinyl.

 

Glen

 

 

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