Ceriatone Plexi 50 Lead build kit Red plating (SOLVED)

Seanxk

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In case the OT is dead, is the hammond 1750N any good?

I would talk to the manufacturer first, you never know, not all companies have a jobs worth attitude, they may even want to help you out, no harm in trying anyway. Report back here with what they say.
 

sdn25

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I would talk to the manufacturer first, you never know, not all companies have a jobs worth attitude, they may even want to help you out, no harm in trying anyway. Report back here with what they say.
I contacted them like a day ago, still no response. Ill keep y'all posted.
 

william vogel

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In case the OT is dead, is the hammond 1750N any good?

Yes, this is a great replacement if it turns out that nick can’t send you another. The Hammond is going to be better than the Ceriatone because it’s primary resistance is nearly identical to the original Drake 784-139. Also check Amp Parts Direct for a Heyboer 8025A-H. The Heyboer is a awesome replacement.
 

sdn25

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Yes, this is a great replacement if it turns out that nick can’t send you another. The Hammond is going to be better than the Ceriatone because it’s primary resistance is nearly identical to the original Drake 784-139. Also check Amp Parts Direct for a Heyboer 8025A-H. The Heyboer is a awesome replacement.
Okay so ive ordered the heyboer 8025A. Either way its fine I guess since I have a better OT now. Maybe Ceriatone will reimburse me for the price of an OT from them idk. Ill update yall on what happens when I install the new OT. And just a big thank you to you all for the help, learnt a lot from this.
 

sdn25

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I have another question that was bugging me recently. Is it possible that my Suhr reactive load had something to do with the damage as well? ie is it possible for a load box to damage the OT? I ran the amp pretty cranked (between 7-9 on volume 1). Or is it certainly the super high bias current that damaged it?
 

neikeel

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Likely a combination of hammering a poorly set up power section into any load.
It’s just like running a car at full throttle for miles and miles with a weak mixture and too much ignition advance - going to hole a piston before long!
 

Pete Farrington

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I don’t see that overdriving the amp into a reactive load would affect it any differently to a speaker cab.
Whereas redplating valves will put the amp under significant stress.
It’s best to regard valves that have redplated heavily as damaged, unfit for further service, unless they can be proved good.
The amp should be protected by a light bulb limiter whilst they are undergoing ‘proving good’ testing.
 
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sdn25

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I don’t see that overdriving the amp into a reactive load would affect it any differently to a speaker cab.
Whereas redplating valves will put the amp under significant stress.
It’s best to regard valves that have redplated heavily as damaged, unfit for further service, unless they can be proved good.
The amp should be protected by a light bulb limiter whilst they are undergoing ‘proving good’ testing.
Right, I shall build myself a light bulb limiter. The tubes that redplated for me are dead. I had done the later tests with new ones.
 

sdn25

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will a 60w incandescent light bulb work well? that's the highest wattage I could find here in singapore
 

william vogel

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Okay so ive ordered the heyboer 8025A. Either way its fine I guess since I have a better OT now. Maybe Ceriatone will reimburse me for the price of an OT from them idk. Ill update yall on what happens when I install the new OT. And just a big thank you to you all for the help, learnt a lot from this.
You need the 8025A-H. It’s the Drake clone. The 8025A is the Dagnall clone. I don’t know the exact difference between the two but the Drake is the classic Plexi’s output transformer and probably has a better interleaving pattern which makes it more expensive. The one you ordered is going to be good but the 8025A-H, I’ve used and it’s wonderful. What are you going to do with the Ceriatone transformer. I’m interested in it. I’ll pay for shipping to get it.
 

sdn25

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You need the 8025A-H. It’s the Drake clone. The 8025A is the Dagnall clone. I don’t know the exact difference between the two but the Drake is the classic Plexi’s output transformer and probably has a better interleaving pattern which makes it more expensive. The one you ordered is going to be good but the 8025A-H, I’ve used and it’s wonderful. What are you going to do with the Ceriatone transformer. I’m interested in it. I’ll pay for shipping to get it.
Correction, I got the 8025A-H. As for the Ceriatone transformer, I don't know. Maybe Ceriatone themselves may ask for it, if not I can send it to you. May I know why you're interested in it? I mean, its dead after all.
 

william vogel

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Correction, I got the 8025A-H. As for the Ceriatone transformer, I don't know. Maybe Ceriatone themselves may ask for it, if not I can send it to you. May I know why you're interested in it? I mean, its dead after all.
I wind transformers and at the very least I want it for the lamination steel. I also would like to unwind it to see if the Ceriatone transformer is wound exactly like the 784-139. I know the correct pattern, wire gauge, etc and I’m always interested to see what different brands are selling as “the Plexi clone”. With the primary resistance measurement you posted at like 15 and 60 ohms, it’s not correct but depending on how it shorted, it’s hard to accurately predict the turns and wire. Unwrapping it is the only real way to find out. I’m also curious if it’s a plastic bobbin or paper formed insulation. I’m pretty certain it’s plastic bobbin because paper insulation is better protection from over current with modern magnet wire. The transformer you ordered is paper insulation just like the early Drake transformers. The later years Drake began using plastic bobbin but with the same pattern. Plastic bobbin is cheaper and faster to wind but the layers get scattered and loose uniformity because the wire gets drawn into spaces that it’s not intended. The paper insulation between each layer gives it a base and separation to achieve perfect coil layers and the varnish impregnates the paper to form an insulation barrier between layers. Here’s a picture of the paper wound.
A2E19CC5-CF78-41FE-ACA7-BDD2BAA33557.jpeg
 

Pete Farrington

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will a 60w incandescent light bulb work well? that's the highest wattage I could find here in singapore
Yes, but for final testing it would need 2 or even better 3 in parallel.
So initial testing (no valves) with a single 60W or lower, then add bulbs as the build / valves prove good, all 3 at 180W for final protected test.
Then switch the limiter to bypass, reset amp bias (as voltage will rise a little) and test at full mains voltage and power output.
 
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Chris-in-LA

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Correction, I got the 8025A-H. As for the Ceriatone transformer, I don't know. Maybe Ceriatone themselves may ask for it, if not I can send it to you. May I know why you're interested in it? I mean, its dead after all.
The 8025A-H sounds really good in one of my JCM800 clones. You won’t be disappointed. But I’m surprised Nik didn’t respond to you, he’s usually really quick and helpful.
 

sdn25

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Yes, but for final testing it would need 2 or even better 3 in parallel.
So initial testing (no valves) with a single 60W or lower, then add bulbs as the build / valves prove good, all 3 at 180W for final protected test.
Then switch the limiter to bypass, reset amp bias (as voltage will rise a little) and test at full mains voltage and power output.
I managed to snag a 100W bulb. Is it possible to do all the testing using just the 100 watter?
 

sdn25

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The 8025A-H sounds really good in one of my JCM800 clones. You won’t be disappointed. But I’m surprised Nik didn’t respond to you, he’s usually really quick and helpful.
Yeah he usually responded quite quick to my emails, idk why he hasn't been responding lately.
 

Pete Farrington

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I managed to snag a 100W bulb. Is it possible to do all the testing using just the 100 watter?
Yes, it's possible, and it's much better than not using a light bulb limiter.
But for the basic / initial no valves testing, 100W may not provide sufficient current limiting to prevent a fuse blowing or even damage, if there's a problem.
And a low power bulb allows the tech to track down a fault whilst it's happening

For testing unknown valves when putting out signal, 100W may drop the mains voltage to the amp too much, and shorts etc that only manifest at high power output remain hidden.
 

william vogel

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I managed to snag a 100W bulb. Is it possible to do all the testing using just the 100 watter?
Sometimes you can find a 200 watt flood lamp. They’re the big ones that go on the corners of the outside of the house. I don’t know if they are used in Singapore.
 

sdn25

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okay so I found a 300w bulb on amazon US but its rated for 120VAC. It is advisable to use that bulb with 240V input?
 

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