During last 6-8 years that I've been using A75 and Zen amps, I had quite a few rectifier bridges failures. It always happened at start up, when one bridge just blew, tripping fuses. I have four A75 and 2 Zens and it happened on all those amps. The fact is, I was using CL-40 as inrush protection (as it was recommended in original article) but my capacitor banks were not really big (80,000u on average). I was also using surplus bridges, however, they were rated 35A.
So now when I'm using that elaborate discreet bridge on my upcoming Aleph X I would like to avoid any future failures and make sure my inrush protection works fine. The total capacitance per channel would be 130,000u. Is CL-60 enough protection? I was experimenting yesterday with resistors, but it looks like with class A amps fixed resistors don't work well, because of a voltage drop. For instance on my A75, 70ohm resistor generated 70V drop and the amp was only receiving 40V AC. So it looks like thermistors are the way to go. I was considering putting two CL-60 in series just to be safer.. Is it worthwile?
This are the bridges I was using so far.
So now when I'm using that elaborate discreet bridge on my upcoming Aleph X I would like to avoid any future failures and make sure my inrush protection works fine. The total capacitance per channel would be 130,000u. Is CL-60 enough protection? I was experimenting yesterday with resistors, but it looks like with class A amps fixed resistors don't work well, because of a voltage drop. For instance on my A75, 70ohm resistor generated 70V drop and the amp was only receiving 40V AC. So it looks like thermistors are the way to go. I was considering putting two CL-60 in series just to be safer.. Is it worthwile?
This are the bridges I was using so far.
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I remember a Nelson drawing of an Aleph 4 on the Passlabs and he used 2 CL 60 in parallel.
So ? Magic 
? Or mistake🙁 ?
So ? Magic ? Or mistake🙁 ?
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Where were the fuses located?
Peter: Sorry I don't have any advice for your problem, but I do have a question. Where exactly were your fuses located that blew when the rectifier would fail?? I'm in the process of building a power supply and want to make sure it is protected from blown bridges...
Thanks,
Eric
Peter: Sorry I don't have any advice for your problem, but I do have a question. Where exactly were your fuses located that blew when the rectifier would fail?? I'm in the process of building a power supply and want to make sure it is protected from blown bridges...
Thanks,
Eric
Peter,
I am using 3 Ohm/20W resistor in series with primary winding of 500VA toroidal transformer.
Pavel
I am using 3 Ohm/20W resistor in series with primary winding of 500VA toroidal transformer.
Pavel
When I tryed to solve the problem with my death NTC I read in one of the thermistor manufactor`s manual (aplication notes), that there is no benefit of useing two paralell conected thermistors on inrush curent protection circuit, since one device will tend to take all the curent flow through the AC or DC rail. Anyway there was a posibility of useing one on AC primary rail and one betwen the bridge and filter caps. Maybe Nelsson can explain what is the purpouse of using two paralel NTC`s in A4. There is only one in A2 for example.
marijan
marijan
CL60's in Parallel
XA-200 uses 4 thermistors in parallel as R element in CRCRC filters.
NP advised that current sharing was not an issue. This must be fairly well proven else Passlabs wouldn't intend to sell these amplifiers to the general public.
XA-200 uses 4 thermistors in parallel as R element in CRCRC filters.
NP advised that current sharing was not an issue. This must be fairly well proven else Passlabs wouldn't intend to sell these amplifiers to the general public.
On the Aleph 1.2 and products that draw more than
about 2 amps, we put Thermistors on each of the
two primary windings, so they aren't literally paralleled.
I use a lot of the 35 amp bridges, and I never see failures,
even with 200,000 uF. Perhaps there is simply something
defective with your surplus bridges.
😕
about 2 amps, we put Thermistors on each of the
two primary windings, so they aren't literally paralleled.
I use a lot of the 35 amp bridges, and I never see failures,
even with 200,000 uF. Perhaps there is simply something
defective with your surplus bridges.
😕
Nelson Pass said:
I guess that must be the only explanation then. Because I had different bridges on my third A75 pair, and indeed no failures there (less caps too, thou).
Eric, I had it mounted on amps heatsinks.
Hi Peter
You can use fixed value resistors for soft turn-on with a class A amp. Just try a lower value. I pick a value that gives me about 80 to 95 volts AC after 10 to 20 seconds on time. If you have a current meter and a variac Ohms law will give you the answer, other wise just try a few different values.
Later
Bruce
You can use fixed value resistors for soft turn-on with a class A amp. Just try a lower value. I pick a value that gives me about 80 to 95 volts AC after 10 to 20 seconds on time. If you have a current meter and a variac Ohms law will give you the answer, other wise just try a few different values.
Later
Bruce
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Peter Daniel said:
Peter, I think you took me too literally: I was interested in knowing where in the circuit did you place the fuses, not where physically.
Some people put the fuse on the primary, others on the secondary, others between the bridge and the caps. Each has an advantage or disadvantage. Just wondering where in the circuit you placed yours...
I thought you asked about bridges.😉 I placed the fuses on primary. I wouldn't put them anywhere else.
Peter,
i bought mine bridges from the chinese store on Queen and from Saya on Victoria Park, are they surplus do you know?
Chris
i bought mine bridges from the chinese store on Queen and from Saya on Victoria Park, are they surplus do you know?
Chris
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Thanks, Peter! I didn't know if placing a fuse on the primary was sufficient to guard against bridge failure... Sorry that you are having trouble with them, but I'm glad to hear that they protect the transformer 😀
Eric
Eric
Eric,
it was sufficient because ea time a bridge blew (at least 6 times for me) the fuses blew too. The fuse is not to protect the bridge, thermistor is taking care of it.
Chris,
I bought them from Sayal, but it was around 1995.
😉
it was sufficient because ea time a bridge blew (at least 6 times for me) the fuses blew too. The fuse is not to protect the bridge, thermistor is taking care of it.
Chris,
I bought them from Sayal, but it was around 1995.
😉
HDTVman said:
I just tried 30 ohm and it gives 30V drop. But things stabilize pretty quick, around 2-3 seconds. About the same as thermistor without trouble of extra relay and required circuit. How did you get 10-20 sec? Must be a different currend draw.
Hi Peter
10 to 20 seconds is with very large C and low current load at turn on (Big Tube Amp). If the power glitches I have to wait for the tubes to cool down before I can bring the amp up again.
Later
Bruce
10 to 20 seconds is with very large C and low current load at turn on (Big Tube Amp). If the power glitches I have to wait for the tubes to cool down before I can bring the amp up again.
Later
Bruce
--defective with your surplus bridges.
Perhaps they are not bin 1's and they
are bin 5's..
whoops, I don't know how many people
will understand what I said.. hehe
Perhaps they are not bin 1's and they
are bin 5's..
whoops, I don't know how many people
will understand what I said.. hehe
Peter,
I would run with the CL 60 but observe your total main current draw.
With my Aleph 2 with 1000va tranni and 120,000 uf supply, the 2 amp slow blow fuse blew repeatedly but not the 35Amp bridge.
Those surplus one you have may not have a high surge rating.
In the end I used the CL60 in conjunction with the simple mains (see earlier thead) derived relay timer to bypass the CL60 after 7 seconds.
This way you are not stressing the CL60 long term and you can re start the amp knowing the CL60 with be cold if needed.
regards
Ian
I would run with the CL 60 but observe your total main current draw.
With my Aleph 2 with 1000va tranni and 120,000 uf supply, the 2 amp slow blow fuse blew repeatedly but not the 35Amp bridge.
Those surplus one you have may not have a high surge rating.
In the end I used the CL60 in conjunction with the simple mains (see earlier thead) derived relay timer to bypass the CL60 after 7 seconds.
This way you are not stressing the CL60 long term and you can re start the amp knowing the CL60 with be cold if needed.
regards
Ian
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