[Theodorus]

Hi , I will try to explain my problem with the Lndverb in english (I'm dutch)
I installed de Lndverb in a home built lightning clone  ,  but the problem is a loud hum.
I have tried to relocate the unit and reverb OT even outside the amp and moved around the wires with no success .(made no difference )
Also turning up the dwell knob is causing oscillation ,
I made a little clip which may be clarifies the problem
https://www.youtube.com/watch?v=F2qQth6HfxA

Hope someone can help me with this
Greetings Theo
 

[Dirk]

Hi,

More informations about what and how you bild would be very helpfull. Please post schematics and voltages, did you check the ground connection etc.

Best regards, Dirk

[Theodorus]

Hi Dirk

The unit is situated after Tonestack (and the 220k resistor) and before PI


Voltage of the B+ is 372V

I measured the three lnd150 mosfet's
                          s             d
first                   0,35 V      231 V
second              0,35 V      340 V
third                  0,35 V      229 V

Reverb tank is : MOD Reverb Tank 8AB2A1B
Reverb OT   is :  Fender Style OT 3,5 W Reverb 125A20B

Ground connections are oké as far as I can tell

Ive tried to use the lower voltage but that made no difference ,

Theo

[Dirk]

The unit is situated after Tonestack (and the 220k resistor) and before PI

If you want to get help than you should supply an exact schematics.

Ground connections are oké as far as I can tell

Yes, that is the problem. Provide an exact schematics including the ground connections will help much more.
How and where did you connect the PSU ?
Maybe some picture would be possible too.

Again: if you want help than you MUST provide all the informations needed to help you. I am no clairvoyant.

Best regards, Dirk

[Athlord]

Moin Dirk,
hast Du gesehen welche Spannung er verwendet?
Er schreibt 372V !
In der Anleitung zum LNDVerb steht doch:

[Dirk]

Moin,

ja, habe ich gesehen, sollte aber kein Problem sein.
Theoretisch kann man auch bis zu 500 V gehen. Die LNDs machen das problemlos mit. Der angegebene Spannungsbereich ist der von uns spezifizierte Bereich, der auch ausgiebig getestet ist und nachweislich stabil funktioniert.
Ich tippe im Moment auf die Spannungsversorgung selbst als Ursache und vermute, dass dies Spannung einfach irgendwo ab B+2 oder 3 abgegriffen wird und das zu Problemen führt. das sst so ein Bauchgefühl aber ohne aussagekräftige Infos kann ich hierzu wirklich nichts sagen.

Gruß, Dirk

[Volka]

Moin,

da würde ich auch drauf tippen... und das Kabelkrams und den Schalter(?) halte ich auch für verdächtig...

Gruß,
Volka

[Theodorus]

Hi
The problem is almost solved , I grounded the PSU ,trafo and wires to the tank to one point and and shortened the power cable to the PSU  now thing are a lot better (still a little hum)


Thanks for your time
Regards Theo

[Dirk]

Looks pretty gold. Please use only one starground and not two.

Best regards, Dirk

[stephan61]

Hi Theo,

Another point:
I see those two powerresistors in parallel with a cap on top. Probably the cathode resistor of the power tubes?
Powerresistors are burning a lot of power and get really hot. The cap located so close to the 2 resistors will get barbecued in short time. I would recommend to move the cap to the side with good distance to the resistors.

Just my 2c

regards
Stephan

[Theodorus]

Thanks for pointing this out Stephan , I realized this when the built was ready .
 The resistors are two 60 Ohm in series instead of the one 120 Ohm that should be there (was not available at that time ) this is going to be changed to make more space for the cap.

Theo

[Volka]

Hi Theo,

keep those resistors: a single resistor (at the same wattage) will get hotter than two. Lifting the Cap 10 millimetres or so from the resistors will do the job...

regards,
Volka

[Theodorus]

Hi Volka , there is some room between the cap and resistors (but not 10mm) , I checked  the temperature after an hour playing (at medium volume) and they did not get hot or even very warm  so I don't think there's going to be trouble  .
So I am just going to leave it like this or maybe put some insulation material between the two (or try to lift it somewhat) just to be sure.
The reverb working fine now after some tweaking of the input and bypass resistors . (I'm in reverb heaven now  )

Thanks for thinking along

Regards
Theo

Picture of the Amp finished :

[Dirk]

The reverb working fine now after some tweaking of the input and bypass resistors . (I'm in reverb heaven now  )

Did you change the chassis grounds too ? I highly recommend it even if you think at the moment that there is no need.

Best regards, Dirk

[Volka]

Hi Theo,

they did not get hot or even very warm

just leave it... no problem