Help troubleshooting CF amps.....

Bob's reply:

Sent: Thursday, March 1, 2012 4:20 PM
Subject: Re: Need help with CarverFest amplifiers, Please!!
Hi Gary, wow, trouble in river city!

First thing is get some good output tubes. The Electro Harmonix are great and have a nice high voltage rating.
Then replace the DC restorer 1n4148 diodes with 1n4004 units. Replace the 15 volt zener with two 5 watt units hooked in parallel. Amp should work then. As for blowing fuses immediately, check the power supply diodes for a short. Use a simple VTVM and just measure them in-circuit. If one shows a dead short, replace it. As for the hum unit, it sounds as if the AC line is somehow connected wrong. Just inspect it careful and I'm sure you will find the problem just by looking hard with your eyeballs. Be careful, because right now I think you may have a severe shock hazard on your hands with this amp until you find the trouble.

If all else fails, send them to me. I'll fix 'em right up!

No sweat,
Bob Carver

What a guy!!! BTW.. I am running the Electro Harmonix in 4 with no issues but addictive sound!!!!

My first question is why were we told to use 15 watt zeners when they are supposed to be 5 watt??

Edit: Sorry, meant to say 15 volt. That's what is in there.

on the bias circuit you need 2 of these....1N5352B 15V 5watt zener
what do you have in there now?

what do you have on the High voltage side of things?
stock diodes are 1N5399

I dont think our amps have a DC restorer circuit. Bob states to change the 1N4148 diodes thet dont exist . Am I right? Is ther a mod for this DC restorer circuit if there is can we get bob to draw it up for us? I would like to add it to my amps.

Bob refers to the DC restoration mod to the bias circuit in his old amps that he is selling on ebay using Zener diodes.

on our amps:
the orig circuit had two 7.5v 1watt Zener diodes in series, these did not work
so now you use two 15v 5watt in parallel.
I dont have the number as my print has a pen mark thru this area and can not see the number.

I bought 2 in53529-tp, thats what bob said to buy way back at the start!! will these work? they are 5w 15 volt?

Mike , A 1n4148 diode is a high speed switching diode in a glass envelope. It is not a zener diode so this is why I stated they dont exist in our amps.

Al, The diodes you have are the correct ones, now get your fucking soldering iron out and put the damn things in already!

on the bias circuit you need 2 of these....1N5352B 15V 5watt zener
what do you have in there now?

what do you have on the High voltage side of things?
stock diodes are 1N5399

The DC restorer is the same you helped me with earlier in this thread; 15 volt/5 watt.

The rectifier diodes on the xformer output are upgraded models based on advice from Mark (radioeng): http://parts.digikey.com/1/parts/106807 ... 100eg.html

Technical/Catalog Information MUR4100EG
Vendor ON Semiconductor
Category Discrete Semiconductor Products
Diode Type Standard
Voltage - DC Reverse (Vr) (Max) 1000V (1kV)
Current - Average Rectified (Io) 4A
Voltage - Forward (Vf) (Max) @ If 1.85V @ 4A
Reverse Recovery Time (trr) 100ns
Current - Reverse Leakage @ Vr 25µA @ 1000V
Speed Fast Recovery =< 500ns, > 200mA (Io)
Mounting Type Through Hole
Package / Case DO-201AD, Axial
Packaging Bulk
Capacitance @ Vr, F -

Mike , A 1n4148 diode is a high speed switching diode in a glass envelope. It is not a zener diode so this is why I stated they dont exist in our amps.

thats because Bob had us take them out,
on mine I killed one when I soldered it in line, then we made a set with longer leads, it worked for a few minutes then the amp red plated.
Bob then cut out the diodes and the amp worked....
this happened on the 1st few amps, so Bob had us not install them as the burnt up....
I dont know if the orig was a Zener

Rectifier Diodes, Harry. They're on the transformer high-voltage output:

I sent these puppies off to Bob today~

Yay!! Thank you for all the hard work on these. Now hook some damn speakers up

Robin, left you a message. I'm getting in the shower, so don't call just yet~