Originally posted by Chuck H
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fender deluxe reverb 65 repair
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Originally posted by Tom Phillips View PostOctal tube sockets are designed with the individual female contacts floating within the body of the socket assembly. Therefore, it is normal for the tube to feel loose. This design feature is purposely done to allow each pin socket to align with the male tube pins while preventing excessive side stress to the tube base.
That's not a great solution because it will raise the high voltage and will also change the character of the amp. It appears that you got a bad new rectifier. Unfortunately, this is fault does happen with modern tubes.
What does it change in the amp with diodes? Tonally i mean...
I always built amps with diodes rectifiers...
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Before the problem the amp has some farting noises or like some fridge noises added to the common hum noise....A noise that appears and desappears after 10 or 20 sec... My first amps were like this i think...
The wiring is not that good, ground points anywhere, long leads, audio and electric wires twisted together...
No HV fuse...
I nearly forgot... I found a broken resistor, a big carbon 470 R 1 watt on the G2 grid position on one tube.
And i had noticed that this 6V6 were more shiny than the other...
I hope the OT is still good...
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The '65 Deluxe Reverb (model AB763) is considered one of the best sounding Fender amps ever made by many players.
I do not recommend to modify the amp..
Rather start troubleshooting:
- Replace power tubes and
- verify schematic voltages.
Can you read schematics?
Do you have a scope?- Own Opinions Only -
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The tone issues are not necessarily related to the rectifier issue. It may just be coincidence and you might have multiple faults with the amplifier.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by tepsamps View PostThe rectifier tube was easy to put and to remove...What does it change in the amp with diodes? Tonally i mean...I always built amps with diodes rectifiers...
Tube rectifiers have inherent series resistance which is much higher than the series resistance of solid state rectifier diodes. Therefore, changing to a solid state rectifier, without making other changes to the amp will result in the following:
1) The DC power supply voltage will increase. The plate voltage of the stock Deluxe Reverb is already high and I personally, don't like to increase it further.
2) Any plate voltage change will require re-setting the bias.
3) Without the sag caused by the resistance of the tube rectifier, the response and feel of the Deluxe Reverb will change. It will be punchier and tighter and produce a little more output power. Only the owner can decide if they like the new feel better. However, the new performance will be a departure from the classic DR.
There are things that can be done to compensate for these effects but that just adds more modification chores.
Keep in mind that Fender could have changed the DR design to use a SS rectifier as the amp evolved over the decades. That would have saved some manufacturing cost without changing the "on paper" specifications. It's notable that they did not choose to do that.
Last edited by Tom Phillips; 10-01-2024, 12:10 AM.
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I won't modify the rectifier... I swear
I have a layout i found on the web, and there are some changes in the power supply in my DR.
First, when i changed the paper cap in the cap room, there were one 10 k and one 2.2 k instead of two 10 k. I put two 10 k 2 watts metal film instead.
I start the amp and it was working good.
So i've changed the rectifier socket, and i tried to stick to the schematic. I changed also the G2 resistors with new ones, but metal film.
I have a lot of checking to do now...Last edited by tepsamps; 10-01-2024, 06:13 PM.
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I try to avoid changing values to match schematics unless I can guarantee someone put in the wrong part in a previous repair. There are too many versions of schematics and what happens in production can vary. Any changes you introduce during the repair process are suspect if you still have problems.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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The amp seems to work fine, but something is weird...
On the chassis, there are marks of heat around the rectifier tube socket and only one power tube socket. So one tube seems to heat less.
I put a 1 ohm resistor on the cahode to ground on both tubes. The bias voltage was -37 V, the hot tube is at 36 mA and the cold one is at only 17 mA, so it's not good for paired tubes.
These are the new tubes i bought recently and it matches the heat marks on the chassis. Tomorrow i switch the tubes to check of course...
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Originally posted by tepsamps View Post... The bias voltage was -37 V, the hot tube is at 36 mA and the cold one is at only 17 mA, so it's not good for paired tubes.
These are the new tubes i bought recently and it matches the heat marks on the chassis. Tomorrow i switch the tubes to check of course...
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The bias voltage is almost the same at pin 5, -35 V. But i took the voltages of the OT, i can't believe what i see
Before swapping the tubes : CT : 448 V Blue : -13 V Brown 442 V
After swapping the tubes : CT : 448 V Blue : -10 V Brown 442 V
The OT is dead ? Why is it working ? The "blue" tube is giving more light than the others ...
Without the tubes : CT 498 V Blue 495 V Brown -3 V ????
And the resistance is 200 R one side, 10 M the other side ???
I can't anderstand how it gives sound and power...Last edited by tepsamps; 10-02-2024, 10:42 AM.
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One side of the OT primary (blue wire) is open, so only one power tube is working and amplifying a halfwave only.
Explains all your symptoms.
The non working tube draws a huge screen current of 17mA, likely causing tube damage.- Own Opinions Only -
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Originally posted by Helmholtz View PostOne side of the OT primary (blue wire) is open, so only one power tube is working and amplifying a halfwave only.
Explains all your symptoms.
The non working tube draws a huge screen current of 17mA, likely causing tube damage.
The replacement is about 60 €... And can be changed fast...
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Originally posted by tepsamps View PostThe bias voltage is almost the same at pin 5, -35 V. But i took the voltages of the OT, i can't believe what i see
Before swapping the tubes : CT : 448 V Blue : -13 V Brown 442 V
After swapping the tubes : CT : 448 V Blue : -10 V Brown 442 V...
It's a good lessen for all of us to keep in mind and it's a rare occurrence to find an open primary winding on an OT.
There is still the possibility that the fault could be where the Blue lead wire is connected to the winding. If so, since that connection is near the outside of the winding stack, you may be able to fix it.
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Hello all,
I have changed the OT, and i still have weird results, not the same ones, but strange.
I tried 2 pair of 6V6, the one i used for the repair, EH, and new ones i just bought, shuagang...
B+ 430 V after the choke 426,5 V bias after the pot -42.5 V
Left Tube Right Tube
Plate 420 422
Grid -36 -40
G2 428 430
K 36.7 mV 26.3 mV
With both pairs of tubes, i have a big unbalance left/right and why G2 voltage is higher than the plate?
And the amp is not silent, but no farting noises
What happens...?
I think i should change the 220 K bias resistors first...Last edited by tepsamps; 10-13-2024, 02:06 PM.
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