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Discussion in 'Shock Brother's DIY Amps' started by Edvin, Apr 9, 2019.
Rookie mistake from me here.
Guess its diodes then. Will 2n4007 be fine?
Oh Hey wait... 2n4007? Maybe not
Ya i ment 1n4007. Just typed too fast again.
I will also need to make a bridge rectifier for the bias here right?
It mesures 39.7vac at 220v mains
I would copy the original bias circuit
+1 on D'tar's recommendation
Make sure you observe the diode and capacitor polarities! You're generating a negative DC bias supply!
With the ~40 VAC bias winding voltage you reported, you will have an approximate range of bias voltages from -30 VDC to -38 VDC. Good luck!
One more comment - D'tar intentionally left out the +/- 16 VDC circuitry also attached to this winding from the original schematic. It serves an entirely different purpose (https://robrobinette.com/Compact_Reverb.htm#Power_Solid_State_Devices) and has nothing to do with your bias supply!
Ya i understood that part.
No offense intended. Observations are as much for other readers (myself included) as the original poster.
Seems like you've made great progress! Good luck!
Sorry if i seemed offended. Im not and are grateful for all help.
It kinda a language barrier i guess. English is not my first language so i kinda speak in short sentences for my own convinence.
I have done a few repairs on amplifiers and built quite a few pedals, so i have some understanding of circuts but building a amp from scratch if a new experience for me.
I thought that might be the case (language), but wanted to play it safe and just reach out - no worries.
Sounds like we're in similar positions - I've had a lot of exposure to electronics (mostly digital), but this amp business is all new to me.
Pleased to meet you, Edvin - "see" you on the forum!
This has really been bugging me:
It took a lot of searching before accidentally stumbling on it in a diagram for a 3-phase motor starter...
So I think this is making sense now. If this is just a thermal overload and does not bring in any additional winding, it would explain why your secondary voltage didn't change when you switched between violet and black/red on your primary input.
Puzzle indeed... Hats off to you, D'tar, for successfully applying your transformer decoder ring to this diagram! As I was searching around for information to better understand it myself, I found a transformer in a Fender '93 Super with the same part number, but featuring a center-tapped bias supply:
and for good measure, the secondary side connection names were also switched around
So im back at this again.
Its been a while since i worked on this mainly cause its become some sort of nemesis, so i have delayed going forward.
But Ive build a brigde rectifier with 1n4007's.
Reading i get:
At 220ac i get 295dc
At 230ac i get 305dc
Isnt that a bit low for a pair of 6L6's?
If you are using a Hot Rod Deluxe power transformer, then you would expect to see similar results as seen in the HRD schematic in the link....under loaded conditions. With no tubes in the circuit, you should see higher voltage as a B+ leaving the rectifier. What is the AC voltage on the red secondaries feeding the rectifier? When disconnected from the rectifier?
Observation: the output of the PT is not necessarily too low for 6L6’s if one designed for such low voltage. And the ProLux...which is in essence a 5E5 Pro which is a 5E3 circuit with different transformers and 6L6’s....should run higher voltage than that if it is true to the vintage Fender approach. The voltages should be lower than the Modern Fenders use, as well...but you are using a modern PT so you will have higher voltage unless you drop some voltage in some manner....once you get the PT and rectifier putting out the voltage they should put out.
Im using the HRD tranny yes.
At 220 i get 324vac
At 230 i get 337vac
According to HRD schematics it should be 431vdc after rectifier.
I use 1n4007 for rectifier not 1n5062 like the original HRD circut.
Something gotta be wrong here.
Edvin, lift the secondarily red wires from their connections and take an AC voltage measurement on across them. What do you read?
The mesurements in last post is with nothing hooked up, just straigt outa transformer.
Variac at 220ac i get 324ac,
Variac at 230ac i get 337ac