Friedman/Ceriatone BE/AHD-50 Clone Build

[Spencerleehorton]

Just set the bias and all looks good, 35mv which = 35ma seems to sit nicely there, made sure i turned all volumes down and no input when testing.
time to do some recording!!

 

[Spencerleehorton]

spoke to soon!!! problem with the fx loop, it has a fx loop from Heikki in there, so not exactly the same as the friedman version and its one ive printed out.

Getting crackling from the loop on the lower strings so somethings not right and the voltages look a bit off?

Voltages for the fx loop as follows:

Q1
C - 36.6v
B - 13.46v
E - 14.02v

Q2
C - 3.63v
B - 1.08v
E - 0.489v

Q3
C - 11.85v
B - 3.63v
E - 3.01v

Q4
C - 36.4v
B - 11.84v
E - 11.27v

Looks like Q1 emitter is down a fair bit as expecting 20v there
Q2 looks about right
Q3 collector is is down should be 20v there
Q4 is also a bit off on the base don’t know what the emitter is meant to be?

I’ll have a look at this 2nd version and trace it all just to make sure its all ok and no mistakes.

I guess the crackles are where the transistors are overloading due to not being biased correctly?

 

[Spencerleehorton]

changed the transistors on the previous version to 2N2222 rather than the BC547C, meant to be drop in replacement when i did a google search but hfe quite different, put back in the first version and seems to work fine now, seems a little noisy but that could be the effects im putting through there, thats the next test in a minute!!!

 

[Spencerleehorton]

Voltage wise the fx loop seems to be where it should be with the bc547c in them

 

[Spencerleehorton]

Had a problem with the mains txf and using a 2A fuse, in rush current too much, needs slow blow 2A, changed today and works fine so far.
Next step, finish line out jack wiring
Then drill out face plates

 

[VanGenz]

I am putting together a very similar amp here in Norway. I bought pcb's and chassis from a russian guy. Just missing the preamp tube sockets and i will finish the amp. Making a 50 watt. Friedman BE-50/100 style amplifier DIY project PCB set | eBay

 

[Spencerleehorton]

Going to put in hi/low switch, need 10A 250vac switch as it needs to handle 450v.
Also going to try and fit in line output jack and pot!!

 

[Spencerleehorton]

Had a little bit if trouble with the line output but sorted it finally, hi low switch is in and tested, did notice a bit of volume fade in and out today which was weird?
Have only put in a 3A switch until the 10A ones arrives.
For some reason I don't hear much if any difference with the texture switch so need to double check.
All other switches seem to work fine and function well.
Just gotta to now take everything off the front and back panels to drill the face plates.

 

[Spencerleehorton]

Spoke to soon!!

Mains transformer is getting very hot!! I dont know how hot it suposed to get but i would say hot to the touch isnt good!!
that must be why its dropping in volume.

Could this be the valves? Mains valves maybe? i have a few others to try and see what voltages look like and see if the transformer runs cooler.

 

[Spencerleehorton]

Could have been bad EL34s but i did also see that there was a wire near the 7812 and the insulation was scorched? this may have not had anything to do with it but im going to remount the 7812 properly to chassis and tidy the cables up!!
seems to behave how it should now, it so damn loud even on the low setting!!!

 

[Spencerleehorton]

still getting volume drops then it sort of stays low volume then jumps up? really strange? does this on either power setting and with or without the fxloop in?
voltages look alright? cant see anything juming around voltage wise?
couple of times the mains txf has got a bit warm which is quite concerning!!?
anyone got any ideas on how to seek this fault out?

 

[Spencerleehorton]

Changed the el34s for a pair I know are good from my plexi build, checked bias for 30-40 minutes, looks good and no volume drops yet.
Will continue to monitor and see if any problem happen.

The fact that the mains txf got warm and the volume drops does point to a dodgy EL34 as it could have a short and that would have caused the problem.

 

[Spencerleehorton]

Just thought I'd say another point about the friedman be50 schematic on the bias the 220k should be 27k and the 25k pot should be 50k.
The schematic resistor and pot values are if you use the HT tap where as the 27k and 50k pot are if you have a 100v winding.

 

[Spencerleehorton]

Still getting volume fades/drops on both channels. Did a gig yesterday and the amp struggled.
Here are the voltages:
V1
Pin 1 - 176.3v
2 - 0v
3 - 1.14v
4/5 - 11v
6 - 160.9v
8 - 0.767v

V2
Pin 1 - 131.2v
2 - 0v
3 - 1.023v
6 - 198v
8 - 1.534v

V3
Pin 1 - connected to Pin 7
2 - 0v
3 - 0.915v
6 - 280.5v
8 - 168.1v

V4
Pin 1 - 222.2v
2 - 24.35v
3 - 38.6v
6 - 207.9v
7 - 25.20v
8 - 38.6v

B+1 - 483v
B+2 - 480v
B+3 - 336v
B+4 - 281.7v
B+5 - 254.5v
B+6 - 176v

Bias = -11.29v
-47v @ 15k/220k
Bias of el34 - 35.6mv

To me it looks like V1 pin1 looks low.
I'm taking the B+ for the fx loop from B+3 I might try moving it to B+4 and see if its makes any difference as it will work from 200v - 350v?

I've ran it with MM on it looking at HT voltage and bias voltage to see if it drops but didn't see anything while the volume dropped?

Any advise on this would be really appreciated.

 

[Spencerleehorton]

I think I've finally found the problem!!
Tested the speakers, 15.1ohms, so no problem there.
Tested the speaker cable, 85ohms!!!
It's quite big diameter speaker cable, a little slither was touching the tip from the sleeve on one end!! Shortened lead now measures only 1.5ohms, made sure to use heartstrings this time, who ever did this lead didn't do it very well, i think it was my late father bless him!!!
Tested it after and no problems and sounds so much better.
Will keep testing but I'm pretty sure the problems I was getting would be caused by this problem.

 

[Spencerleehorton]

Revisiting this build and making a few changes as an x military guy I know has had a look and made some very good suggestions to help it all be better.
Re flowing all joints and removing 1n4007 and replacing with 1n5408.
Also re flowing all bus bar connections with hotter iron and building another turret board for the 100uf/600 section, I'm using 4 x 47uf/600v.
Cleaning up all the gnd connections and need to look at the fx loop as the pcb I e made makes a noise when I tap it so something isn't right.
Gonna work through the list and see if it all improves.

 

[Spencerleehorton]

Have mounted sub board and re soldered most of the gnd connections and buss bar.
Missing a cap as a leg snapped off!!
Ordered a new one.
Gonna change the diode bridges to 1n5408.
Have also tested the output txf and the windings didn't test as originally advised by the company who sold it too me!!!
No wonder I was seeing some ringing and the txf were getting a bit warm!!
Going to also cut a nice bit of venting in the rear wooden back and put in some grills.
Was also thinking of putting in a 12v fan but I'll see how it tests first!!!

 

[Spencerleehorton]

Powered up and amp is sounding much better, my main problem now is the fx loop which I've built, a design from another forum user, I'm sure it's a good design but I have had problems with it from the start and tonally from it in or out there is such a big difference so I'm going with another design as per the original fx loop for the friedman.
Need to make some vent holes in the rear panel and put in the aluminium mesh which I've got.
Used the amp for about an hour today and the mains txf was cool as a cucumber!
Once I've got the new fx loop in I'll do a several hour test to make sure all frequencies are good and the amp doesn't get hot.

 

[Spencerleehorton]

I built two fx loops and have taken out the first one which is having problems and moved the B+ node to a lower node now at around 250v rather than at 285v.
I've put in the second fx loop and powered up and initially on a little test this morning tonally sounds good and a good volume match with it in and out.
Will cut the vents out now and put the grills in then put on a soak test.
Re wiring the output txf wires I hope has improved it as well as I think the txf company had told me the wrong wire colours as they tested differently to what they had told me.
This could have been a problem along with some cold solder joints and the gnd wiring.

 

[john12ax7]

Vents above the power tubes are a good idea. That should be enough, you shouldn't need a fan.

Fx loops are tough to get right, they usually mess up the tone too much. I'ld ditch that if you don't really need it.