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 Post subject: Old Rectifier?
PostPosted: Jun Wed 06, 2018 6:28 pm 
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I got this old powered speaker/amp. I've never seen a rectifier/diode like the one that is in it and I am hoping somone might be able to shine some light on it. It take in 156.5 vac and outputs 141.2 vdc, but I am also seeing about 13.5 vac coming out too. I'm assuming it's failing or perhaps these just weren't real efficient?

Here is the info of the part: BJ11 1L RR Co.
I attached a couple pictures...

Attachment:
What is this part (2)(small).JPG
What is this part (2)(small).JPG [ 119.41 KiB | Viewed 2524 times ]


Attachment:
What is this part (3)(small).jpg
What is this part (3)(small).jpg [ 102.59 KiB | Viewed 2524 times ]


Thanks for looking, etc...


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Wed 06, 2018 7:34 pm 
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Hi, and welcome aboard.

That's a standard selenium rectifier.

The 13vac you're seeing is because the filter caps have degraded.
The same is true of the rectifier itself. Both should be replaced.

You can use any modern silicon rectifier with proper specs.
I normally use 1N4007, which is rated 1 amp @ 1000 volts PRV.

The 180-ohm resistor attached to one terminal is important and should be retained.
It limits surge current into the filter capacitor at turn-on.

- Leigh

On edit: The original post had the wrong diode number ;-(

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Last edited by Leigh on Jun Wed 06, 2018 7:58 pm, edited 1 time in total.

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Wed 06, 2018 7:55 pm 
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Leigh wrote:
Hi, and welcome aboard.

That's a standard selenium rectifier.

The 13vac you're seeing is because the filter caps have degraded.
The same is true of the rectifier itself. Both should be replaced.

You can use any modern silicon rectifier with proper specs.
I normally use 1N4148, which is rated 1 amp @ 1000 volts PRV.

The 180-ohm resistor attached to one terminal is important and should be retained.
It limits surge current into the filter capacitor at turn-on.

- Leigh

I think you mean a 1N4007. The 1N4148 is a small signal diode rated at 100v/200mA.
John

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Wed 06, 2018 7:58 pm 
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OldWireBender wrote:
Leigh wrote:
Hi, and welcome aboard.

That's a standard selenium rectifier.

The 13vac you're seeing is because the filter caps have degraded.
The same is true of the rectifier itself. Both should be replaced.

You can use any modern silicon rectifier with proper specs.
I normally use 1N4148, which is rated 1 amp @ 1000 volts PRV.

The 180-ohm resistor attached to one terminal is important and should be retained.
It limits surge current into the filter capacitor at turn-on.

- Leigh

I think you mean a 1N4007.

You're right.

I did mean the 1N4007.

Sorry for the error. Senility rears its ugly head. Thanks for catching it.

- Leigh

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Wed 06, 2018 8:22 pm 
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Thanks you guys. Great information. I originally was looking at TubesAndMore.com for another firecracker type capacitor, but I think I am going to use a terminal strip and two caps being there is enough room - it'd be reversible if someone else want to go back to a firecracker type too.

Edit Starts Here:
I'm thinking about replacing the present rectifier with a full wave rectifier. I have a few on hand and they aren't much bigger than whats in it. Any thought on that? This is a nice condition all original speaker/amp. I'd like to keep it original, but I really want to use it, so I also want it functional and as quiet as possible.


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 1:28 am 
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What sort of speaker-amp is this? A link to a schematic would be really nice. The tube line-up might tell us what we need to know to help you.

Can't tell from the photos if this rectifier is providing grid bias for push-pull parallel KT-88s, or plate voltage for a lone 60FX5.

Ted


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 1:32 am 
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AleutGerl wrote:
I originally was looking at TubesAndMore.com for another firecracker type capacitor

Could you please post a photo of a "firecracker" capacitor.

I have no idea what that might be.

- Leigh

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 2:18 am 
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I bet the firecracker cap referred to is just a dual section electrolytic cap with long leads protruding out the ends. Some had red cover paper and so looked like a large firecracker. Using a terminal strip mounted to the chassis with individual caps works just fine. I've done just that a few times.


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 2:39 am 
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A bridge rectifier may cause grounding problems; it depends on the circuit. A schematic would help

A firecracker capacitor is one that was connected backwards. :lol:

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 3:06 am 
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Jim Mueller wrote:
A bridge rectifier may cause grounding problems; it depends on the circuit. A schematic would help

A firecracker capacitor is one that was connected backwards. :lol:


It can also be a bottle rocket when they fall into the solder wave pot.


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 4:50 pm 
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RR is Radio Receptor Co. 8J1 was one of their popular products, a 65-mA half wave rectifier designed for 130-V RMS input (380-V PIV). They were specifically intended for powering five-tube AC/DC radios. The 1-1L in the part number probably refer to the bracket attached to it, which was not on the standard devices.

The fact that you are seeing approximately 140 volts DC out of it suggests that the rectifier is still working properly. Many of them still do. Whether you replace it or not depends on what you plan on doing with the speaker/amp. If you are going to put it on a shelf as an antique or collectible item and only use it on rare occasions, there's little harm in leaving the old rectifier in place. But if you are going to put the unit back into regular service, you'll probably find a 1N4007 diode less troublesome in the long run.

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 07, 2018 5:39 pm 
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That appears to be a single rectifier. Not sure how you would use a full wave bridge to replace it unless Just wiring the bridge to use only one of its diodes....

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Tue 12, 2018 8:56 pm 
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AC on the DC output might be just ripple voltage. An AC meter on the output of a DC rectifier may give you a misleading idea of what you are seeing.

Pete

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 10:58 am 
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Usually Lurking wrote:
What sort of speaker-amp is this? A link to a schematic would be really nice. The tube line-up might tell us what we need to know to help you.

Can't tell from the photos if this rectifier is providing grid bias for push-pull parallel KT-88s, or plate voltage for a lone 60FX5.

Ted


Sorry - got side tracked away from doing hobby stuff for a while. I've attached a schematic of it.


Attachments:
Allied Knight KN4160 (radio forum).pdf [122.06 KiB]
Downloaded 64 times
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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 11:00 am 
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Leigh wrote:
AleutGerl wrote:
I originally was looking at TubesAndMore.com for another firecracker type capacitor

Could you please post a photo of a "firecracker" capacitor.

I have no idea what that might be.

- Leigh


Here is a link to the capacitor: https://www.tubesandmore.com/products/c ... ectrolytic


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 11:02 am 
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dacsman wrote:
I bet the firecracker cap referred to is just a dual section electrolytic cap with long leads protruding out the ends. Some had red cover paper and so looked like a large firecracker. Using a terminal strip mounted to the chassis with individual caps works just fine. I've done just that a few times.


Ya, it's just an old school looking multi-cap. I will be going with two separate caps as the originals seem to have bee a little under rated for the voltage across them.


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 11:06 am 
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Chris108 wrote:
RR is Radio Receptor Co. 8J1 was one of their popular products, a 65-mA half wave rectifier designed for 130-V RMS input (380-V PIV). They were specifically intended for powering five-tube AC/DC radios. The 1-1L in the part number probably refer to the bracket attached to it, which was not on the standard devices.

The fact that you are seeing approximately 140 volts DC out of it suggests that the rectifier is still working properly. Many of them still do. Whether you replace it or not depends on what you plan on doing with the speaker/amp. If you are going to put it on a shelf as an antique or collectible item and only use it on rare occasions, there's little harm in leaving the old rectifier in place. But if you are going to put the unit back into regular service, you'll probably find a 1N4007 diode less troublesome in the long run.


Thanks for the info. I'm hoping to make a regular user table top type amplifier.


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 11:08 am 
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Peter Bertini wrote:
AC on the DC output might be just ripple voltage. An AC meter on the output of a DC rectifier may give you a misleading idea of what you are seeing.

Pete


I've already tested it with a single diode (half wave) and with a full wave and I got 1 volt difference. The full wave is just providing much less pulsating DC (ripple).


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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 3:10 pm 
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AleutGerl wrote:
Peter Bertini wrote:
AC on the DC output might be just ripple voltage. An AC meter on the output of a DC rectifier may give you a misleading idea of what you are seeing.

Pete


I've already tested it with a single diode (half wave) and with a full wave and I got 1 volt difference. The full wave is just providing much less pulsating DC (ripple).


Just curious, did you keep the 180 ohm resistor in series with the new rectifier?

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 Post subject: Re: Old Rectifier?
PostPosted: Jun Thu 21, 2018 8:35 pm 
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Thanks for the schematic link!

This is a "one tube" audio amplifier. Two stages. It does have a power transformer.

The B+ supply was half wave using the selenium rectifier. 160V filter caps imply a pretty low B+.

Since the AC source for the B+ supply is an isolated transformer winding, a four diode bridge is OK to use in place of the old selenium.

Using the bridge should reduce hum, and also reduce heating in the transformer.

With a silicon bridge, it would probably be safe to reduce or eliminate the 180 ohm series resistor. The transformer will provide enough series impedance to keep peak currents reasonable.

You might want to go to 250V filter caps.

Ted


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