Hey all,
I have a pair of Quickie 8417 amps - the two rectifier version. It was returned and modded by Quicksilver for all other tubes (as said by previous owner), and currently fitted and biased for 6550 @ 70ma each pair.
Anyway with that huge 390uf cap after the rectifier, I pulled the parallel pair of 5AR4 and dropped in one of my DIY SS rectifiers (an empty octal base with two series UF4007 from pin 6 to 8 and another pair of series UF4007 from pin 4 to 8, and base filled with hot wax). Don't really see an improvement in sound, but I just don't like seeing those expensive 5AR4s getting tortured...anyway, there is a rather hard and noisy start up from the power transformer...looking at putting in a CL60 or CL90 on tranny primaries...or better simpler option?
Also any advice for quieting the mechanical noise from Transformers? These two amp transformers have to be the noisiest I have ever had...
Also noticed it still does not have a Chassis ground...odd that the factory didn't bother adding it... I will add either way...
I have a pair of Quickie 8417 amps - the two rectifier version. It was returned and modded by Quicksilver for all other tubes (as said by previous owner), and currently fitted and biased for 6550 @ 70ma each pair.
Anyway with that huge 390uf cap after the rectifier, I pulled the parallel pair of 5AR4 and dropped in one of my DIY SS rectifiers (an empty octal base with two series UF4007 from pin 6 to 8 and another pair of series UF4007 from pin 4 to 8, and base filled with hot wax). Don't really see an improvement in sound, but I just don't like seeing those expensive 5AR4s getting tortured...anyway, there is a rather hard and noisy start up from the power transformer...looking at putting in a CL60 or CL90 on tranny primaries...or better simpler option?
Also any advice for quieting the mechanical noise from Transformers? These two amp transformers have to be the noisiest I have ever had...
Also noticed it still does not have a Chassis ground...odd that the factory didn't bother adding it... I will add either way...
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I solved a similar transformer noise problem widening the holes under it a little, putting grommets in there. The trannies were now isolated from the chassis and the noise was gone.
Concerning the power supply, why not use a somewhat smaller input cap? With 100mu you won't destroy your 5AR4's and that little bit of extra ripple you might get (although I doubt that) will be nulled because it's a pp output stage.
Concerning the power supply, why not use a somewhat smaller input cap? With 100mu you won't destroy your 5AR4's and that little bit of extra ripple you might get (although I doubt that) will be nulled because it's a pp output stage.
So I put in a single CL-60 on the hot mains feed to fuse, put in that ground wire to the power trannie screw post, and also put in rubber donuts (o-rings for faucets found at hardware stores) on all four transformer screws...now quiet startup and quite a bit less transformer vibration...all good!
If you put the diodes you will get a inrush current very high , this is the noise.
And the power trafo is under stress each time you power the amp.
With GZ34 the current goes up slowly because the tube is an indirect rectifier. Even the cap are too high for this every type of tube rectifier.
Then you will have more Vdc with diode on all circuit and you have to check the bias and the performance of the entire amp
One solution can be to put a Ntc with 4-6 A and around 50 ohm in series with primary of the power trafo to lower the intial peak
And the power trafo is under stress each time you power the amp.
With GZ34 the current goes up slowly because the tube is an indirect rectifier. Even the cap are too high for this every type of tube rectifier.
Then you will have more Vdc with diode on all circuit and you have to check the bias and the performance of the entire amp
One solution can be to put a Ntc with 4-6 A and around 50 ohm in series with primary of the power trafo to lower the intial peak
Hello all, one more Q - if I add the series Diodes (UF4007) to the input of the two 5AR4 rectifiers, do I still need to be concerned about the 320uf cap right after the 5AR4?
Per spec sheet, the max capacitor after the two 5AR4 rectifier tubes should be 60uf x 2 = 120uf....again, don't wanna kill these expensive 5AR4 tubes...
Per spec sheet, the max capacitor after the two 5AR4 rectifier tubes should be 60uf x 2 = 120uf....again, don't wanna kill these expensive 5AR4 tubes...
No It isn’t the right way
I repeat to consider a proper Ntc
Or a delay circuit always in series with primary
10 sec can be enough
I have already installed the CL60 on the tranny primary and works great.
Now in addition to the CL60, adding series diode to save the rectifier - is it needed?
Now in addition to the CL60, adding series diode to save the rectifier - is it needed?
I have done amps with a Gz34 with the first cap at 47 uF + inductor 10 H + 4x 220 uF.
They ran for years without any problem
Of course the 34 were nos/nib
They ran for years without any problem
Of course the 34 were nos/nib
Hi
I haven't read carefully you post nr.3.
Have you checked the time to get the 0 volt across CL60? And how is the max peak voltage after power on?
I think that one Ntc is fine for the job.
But Is better to check the +Vdc delivered with diodes to the circuit
It will be higher than 34
I haven't read carefully you post nr.3.
Have you checked the time to get the 0 volt across CL60? And how is the max peak voltage after power on?
I think that one Ntc is fine for the job.
But Is better to check the +Vdc delivered with diodes to the circuit
It will be higher than 34
UF4000 series diodes don't have all that great of an inrush rating. A better choice would be the IN5407G or FR307. The iN5407G has a guaranteed reverse recovery time of 2 us, and is a premium version of standard 1N5400 parts series.
Each Transformer rectifier lead connects to one 5AR4 rectifier (one lead to both pin 4 and pin 6 on each rectifier),
I now have connected each lead to a UF4007 to pin 4 and another UF4007 to pin6, on both tubes, so seeing 1/2 the duty.
Also have the CL60 limiting inrush.
The 5AR4s are likely providing enough delay so that you don't see the initial inrush, with the UF4007s picking up the slack as the tube rectifiers warm up.
The uf 4007's are superfluous here. You put the UF's in series with the 5AR4 diodes; they don't protect the tubes. The inrush current limiter prevents the 5AR4's from being destructed by the 320mu cap.
Without the CL60 you could either use
- merely the UF's and the 320 mu cap
- or the 5AR4's and max 120 mu