Is my 5E3 sick ?

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Hebaton
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Is my 5E3 sick ?

Post by Hebaton »

Just recently got a 5E3 in a trade. took it home started playing around with it and found some nice tones.. then I realised I could get absolutely zero clean headroom with the guitars I have ( all Humbuckers )
From what I have read, this thing should be loud enough to play with a small band ...not a very loud band but still. And guys say they can get nice cleans at usable volumes with them before they go into OD.
I changed all the tubes, installed a Jensen P12Q and I certainly can turn this thing way up in the house without my wife taking notice ( nice way of putting it )

Can someone point me to point and voltages I could verify ? The build looks well executed but the results ???

P.S. I am nbot a tech and my knowlage of electronics is very very limited. I did realise and succeded with simple amp mods with the help of good info and grafical support tough...
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

Come to think of it, I did not replace the rectifier...
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Re: Is my 5E3 sick ?

Post by TriodeLuvr »

Does it distort when you turn it up?

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Daviedawg
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Re: Is my 5E3 sick ?

Post by Daviedawg »

My experience of 5E3s built to original Fender schematic is that they are very loud at low volume settings and are crunchy pretty much as soon as you move beyond 1 on the dial. I cannot play mine at home over half way between 1 and 2 on the dial. They don't get a lot louder but get more distorted beyond 50% of volume setting. Mine is mostly run through a Celestion G12/50 yellow frame which is not as efficient as more recent speakers. For clean tones you need to turn humbucker volume down. Less so with single coils which is what I play mostly through it.

6V6 voltages at plate and screen are 352 and 313. At the cathode is 20v. 12AX7 pins 1 and 6 are 156 and 187. For the 12AY7 110 and 130v. Those are the only voltages I still have recorded as it was a few years ago I built it. It has a 5Y3 rectifier.

Just for interest VVR does not work well with this circuit but attenuators do.

Dd
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

Daviedawg wrote:
Sun 07/11/21 2:33 am
My experience of 5E3s built to original Fender schematic is that they are very loud at low volume settings and are crunchy pretty much as soon as you move beyond 1 on the dial. I cannot play mine at home over half way between 1 and 2 on the dial. They don't get a lot louder but get more distorted beyond 50% of volume setting. Mine is mostly run through a Celestion G12/50 yellow frame which is not as efficient as more recent speakers. For clean tones you need to turn humbucker volume down. Less so with single coils which is what I play mostly through it.

6V6 voltages at plate and screen are 352 and 313. At the cathode is 20v. 12AX7 pins 1 and 6 are 156 and 187. For the 12AY7 110 and 130v. Those are the only voltages I still have recorded as it was a few years ago I built it. It has a 5Y3 rectifier.

Just for interest VVR does not work well with this circuit but attenuators do.

Dd
Thank you. I'll compare those voltages with what I am getting on mine. I am sure something is off.
What would cause such an amp to be weak ? mine is definitely not loud. I have an AC15 there is simply no coparaison in terms of loudness. THe VOX will get the neigbers ragaing but the 5E3 wont even bother my wife iin the next room...
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Daviedawg
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Re: Is my 5E3 sick ?

Post by Daviedawg »

The voltages might give us a clue as to what is wrong or at least what is right and where to start looking. Be sure to include the voltage after the rectifier as well as on the other valves.

Dd
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

Here are the readings I am getting:12AY7 pins 1 and 7 >118 - 120 on the 12AX7 I get > 163-193
ON the 6V6 plate and screen 366-320 cathode is 19.7

ALl that seems O.K. I am starting to beleive the issue with the "new" speaker ( Jensen P12Q )
Buy the way this is an ineffective speaker at 94.4 DB for 1W/1M according to plublished spec.
I have a 16 ohms Alnico blue at 101 DB but I'm not sure what thawill tell being so different and how much it would stress the OT ???
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

Daviedawg wrote:
Sun 07/11/21 5:52 am
... Be sure to include the voltage after the rectifier as well as on the other valves.

Dd
I'm afraid my very limited knowlage does not allow me to know what that means.
Would you please explain ? where would be the point to take those readings from ?
ANd How can I check biais on this amp ?
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Daviedawg
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Re: Is my 5E3 sick ?

Post by Daviedawg »

This amp is cathode biased so the voltage readings at the 6V6s tell us how it is biased.
The voltage from the rectifier can be measured by taking the reading between the positive node of C1 (which is the first 450v electrolytic capacitor) and ground. If in doubt which is C1, take readings at all the large electrolytics and see which has the highest reading.
Of course there are high voltages so you need to be careful.
I doubt if the issue is with your speaker. Even the lowest efficiency will sound louder than you have described.
Can you take some pictures of the internals at good resolution and post them here?

Dd
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

I'll get the readings but here are some pics.
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

According to my readings:
Voltages at C1 363, C2 313, and C3 260

I also noticed that, interaction between the two volumes seems to be less then what is usually described.
The posistion of the Normal channel volume has no effect on the sound, when plugged in the Bright channel,until the very end of it's travel ( when reaching 11 and 12 ) then it significantly limits gain and volume. But the action is very sudden at that point and not progressive.

Can it be determined just from the looks, if quality parts were used or if this is a collection of cheaps ones ?
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

I beleive found something.
THe 5E3 Schematic calls for 56K resistors at R3, R4, R5 amd R6
ON mine, all read 34K this must have some influence no ?
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Re: Is my 5E3 sick ?

Post by Daviedawg »

Thanks for the pics. I will look at them later. Have you tried swapping valves? I should have mentioned that first, sorry. What make and age of preamp valves are under the cans?
First stop next I would suggest is ensuring the valves are ok. If you have spares swap one at a time to see if that makes a difference. Even pulling out and replacing the same ones may expose oxidation of pins if the amp has been sitting for a while. Do you know how old it is?

Dd
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Hebaton
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Re: Is my 5E3 sick ?

Post by Hebaton »

Daviedawg wrote:
Sun 07/11/21 1:07 pm
Thanks for the pics. I will look at them later. Have you tried swapping valves? I should have mentioned that first, sorry. What make and age of preamp valves are under the cans?
First stop next I would suggest is ensuring the valves are ok. If you have spares swap one at a time to see if that makes a difference. Even pulling out and replacing the same ones may expose oxidation of pins if the amp has been sitting for a while. Do you know how old it is?

Dd
I have replaced all but the rectifier and they were tested in another amp as well. DId you notice what I just wrote about the resistors ?
... I beleive found I something.
THe 5E3 Schematic calls for 56K resistors at R3, R4, R5 amd R6
ON mine, all of those read 34K this must have some influence no ?...
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Re: Is my 5E3 sick ?

Post by Daviedawg »

The Fender schematic does not reference the resistors by numbers. So I am not sure which those might be. I have only two 56ks one of which is the plate resistor at pin 6 of the 12ax7 so would not make a huge difference to the output if it were a 34k. The other is the cathode resistor related to that and again the amp would not be greatly affected in terms of output.
Four resistors that are the same value are the 68ks at the input jacks which when paralleled in two positions are 34k of course. But again that is not going to be your issue. So I would not be concerned about that at this point.
Sounds like the valves are not the problem. So I will take time later to look at your pics for any clues as to the problem.

Dd
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