DBT with 2 indescendent lamp 60W in parallel for checking amp 150wpc possible?

[diepbtt]

I just recapped an amp with power consumption 400W/110V and now want to test it with DBT.

Someone suggests using 100W/120V as suitable for such amp with mentioned 150wpc.
Unfortunately i can get 60W/127V for this testing purpose in my country only.

But i read somewhere that i could build a DBT using 2 lamps 60W wired parallel for the same result as using only one lamp 100W.

Could someone with knowledges/experiences confirm it is possible or wrong?

Thank you in advance.

 

[Hyperion]

It isn't ideal - but it will work.

 

[diepbtt]

It isn't ideal - but it will work.

Thank you for reply.
Of course i want to use only one lamp 100W as DBT but it is very difficult to get a lamp with supply voltage 100V/110V /120V in my country with general power supply 220V.

Fortunately i found two lamp 60W/127V left in a shop after seeking i all shops throughout my country.

So i must use this solution though it is not ideal as you suggested.

Thank again!

 

[restorer-john]

No, you shouldn't be using a 127v globes on a 220V supply at all!

You use globes that match your supply voltage.

Put the DBT with 220v globes (a 60watt would be fine) on the primary side of your stepdown transformer (I assume you are using a stepdown to power the amp as you state it's a 110v amp)

 

[diepbtt]

I thought the DBT was used as a precaution to current limit (and light up) in the event of a fault which would otherwise draw a lot of current and cause a lot of damage.


Yes i think it also.


What are we trying to accommodate here with the bulb wattage? Are we going to crank it up to 400 watts of draw and see if the primary AC sags and the bulb(s) come on? I have no idea, therefore the question.


No i want to check the amp at idle after recapping only whether any shorts or not. Not the amp at full power!

The specs. given are for consideration the suitable wattage bulb for best result.



edit: I may end up answering my own question but here are the guidelines from the sticky:[/QUOTE]

Thank you for your suggestion. I have read it already.

 

[diepbtt]

No, you shouldn't be using a 127v globes on a 220V supply at all!

You use globes that match your supply voltage.

Put the DBT with 220v globes (a 60watt would be fine) on the primary side of your stepdown transformer (I assume you are using a stepdown to power the amp as you state it's a 110v amp)

Maybe we interprete wrongly.
I have a amp 400W/100V recapped and want to test with DBT.
of course i have a step-down transformer from 200V to 100V/110V. for testing the amp with DBT using 110V output.

The problem is that i can lamp 60w/127V ( no higher wattage lamp) only in my country where the power supply is 220V 50Hz this means it is difficult to buy any lamp with power supply.

For an amp with 400W/100V, 150wpc is the lamp 60W/127V not very suitable.

I have read it should be with lamp 100W or higher wattage as suitable for testing the amp with above mentioned specs.

But you know that i can not get such 100W or higher wattage lamps.

So als altenative as someone writes on the net i can build the DBT with 2 lamp 60w/127V in parallel in order to get as a lamp with 100-120W for my testing purposes.



My question is therefore whether it is correct or not.


Today i have tested this amp with DBT at 110V power supply( from step-down transformer) with following results:
DBT with one lamp 60w in series with the amp: the globe glows a bit

DBT with two lamp 60w wired paralell each other but in series with the amp:
both lamps light 3-5 second then dim consideringly.
A bit longer then the relay clicks.


I have almost same results by testing other amp( with full normal function) with specs. 280w/100V as the lamp in both cases are more dimmly:
DBT with two lamp 60w wired paralell each other but in series with the amp 280w/100 :
both lamps light 3-5 second then dim consideringly. The relay can click!

So i think my recapped amp 400W/100V 150wpc may be OK or shouls i test it further with DBT with 200w lamp?

 

[restorer-john]

It seems like your amp is fine if the DBT is behaving the way you describe.

 

[diepbtt]

It seems like your amp is fine if the DBT is behaving the way you describe.

Thank you
Here is the pictures of my DBT after some seconds (sorry for the mess due to my hasitation):
amp: Trio KA-9900 400W/100V ( or Kenwood KA-907) and Trio KA-8700 280W/100V( currently use OK regularly)

power supply: 110V 50Hz from stepdown transformer

DBT: 2 lamp 60W/127V wired parallel each other but in series with the amp

I hear the relay clicks and no smokes!

But i have further question what is the result when i connect 2 lamp 60w in series as DBT?



Update:
The amp direct to AC supply 100V plugged , 4-5 seconds then relay click, no magic smokes and i can adjust DC offset for tone control/power amp almost to 0.1mV and Bias current 20mV as shown in the sm.

Thank all for helping me.

 

[restorer-john]

Putting the globes in series will cause the dbt to behave strangely I would expect with inconsistent 'glowing' and dropping more voltage than we want, resulting perhaps in amps not functioning at all, or erratic operation.
Stick with one bulb where you can, matched to suit the device and all will be fine.
I use 15,25,40,60,75 and 100 watt bulbs for everything from turntables right through to power amps. Even a 350 watt per ch power amp can be fired up on a 75 watt bulb and be operational for low level testing.

 

[diepbtt]

Putting the globes in series will cause the dbt to behave strangely I would expect with inconsistent 'glowing' and dropping more voltage than we want, resulting perhaps in amps not functioning at all, or erratic operation.
Stick with one bulb where you can, matched to suit the device and all will be fine.
I use 15,25,40,60,75 and 100 watt bulbs for everything from turntables right through to power amps. Even a 350 watt per ch power amp can be fired up on a 75 watt bulb and be operational for low level testing.

Thank you for your explanation.
Of couse we follow the DBT using instruction you mentioned.