:I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

The unit has 2 resistors in a perforated metal enclosure that measures 4" long, 3" wide, and 2" tall with 2 slotted mounting ears. Weight is 1 pound. One resistor has a slider to adjust the resistance. I have used these to drop 12 volts to 6 volts for a typical 6 to 8 amp vibrator powered radio. They do get hot, which is the reason for the metal enclosure.

Cost for you would be actual shipping cost only. I tried to email you but it bounced.

Meade

:Does this unit have a heat sink to absorb the warmth. It should fit uner the dash out of site and in line with the A+?? How much? I am meeting with the owner in abit and will let him know. Thank you.

Del: I would use a series pass transistor such as a 2N3055 which is in a TO3 package and mount it to the chassis for heat sinking. You can bias the base using a 7 volt zener diode which would make the output about 6.3 volts and it would be regulated as a bonus. You can find these simple series pass transistor circuits in numeous references and they require only a few parts. It will be necessary to insulate the transistor from the heat sink. Your radio should draw about 7 amps or so when playing. Good Luck.

What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
Doug

:I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

:Del: String three silicon diodes in series - each one drops 0.7V. Total cost less than $1. And they don't get hot like a resistor.
:
:What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
:Doug
:
:
::I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

You don't need fancy diodes, like FREDs, etc. - just garden-variety silicon diodes.

You could get a 6-V zener, and put that in series between the 8-V battery and the radio. But you still need to size the zener to handle the maximum wattage dissipation in the diode.

The radio's fuse size might not be indicative of the normal current to the radio? Maybe by inspecting the schematic you can guesstimate the current draw?

Is this a 6-V radio? Then you could hook it up temporarily to a 6-V supply, and measure the current draw with your DMM. You can use three or more "sacrificial" silicon diodes in series with the 8-V battery for testing.

By the way, how come you are using an 8-V battery?

Heat sinks aren't available for many diode packages. The power dissipation will be 0.7V times whatever the forward current is. You need to buy diodes that can handle the current.

You may need beefier diodes, and put them in parallel?

Homework time. Google is your friend, along with whatever books you have.
Doug

:Radio uses a 14 amp fuse as per schematic. Do I need a heat sink? I cannot find .7v diodes.
:
::Del: String three silicon diodes in series - each one drops 0.7V. Total cost less than $1. And they don't get hot like a resistor.
::
::What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
::Doug
::
::
:::I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

ALL garden-variety silicon diodes have a 0.7V forward voltage drop. Diodes, forward biased, are often used for DC voltage supplies.
:
:You don't need fancy diodes, like FREDs, etc. - just garden-variety silicon diodes.
:
:You could get a 6-V zener, and put that in series between the 8-V battery and the radio. But you still need to size the zener to handle the maximum wattage dissipation in the diode.
:
:The radio's fuse size might not be indicative of the normal current to the radio? Maybe by inspecting the schematic you can guesstimate the current draw?
:
:Is this a 6-V radio? Then you could hook it up temporarily to a 6-V supply, and measure the current draw with your DMM. You can use three or more "sacrificial" silicon diodes in series with the 8-V battery for testing.
:
:By the way, how come you are using an 8-V battery?
:
:Heat sinks aren't available for many diode packages. The power dissipation will be 0.7V times whatever the forward current is. You need to buy diodes that can handle the current.
:
:You may need beefier diodes, and put them in parallel?
:
:Homework time. Google is your friend, along with whatever books you have.
:Doug
:
::Radio uses a 14 amp fuse as per schematic. Do I need a heat sink? I cannot find .7v diodes.
::
:::Del: String three silicon diodes in series - each one drops 0.7V. Total cost less than $1. And they don't get hot like a resistor.
:::
:::What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
:::Doug
:::
:::
::::I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

6-A diodes - four for $2.49. Put three pairs in parallel, then put those in series. You put the parallel/series string in the circuit between the battery and the radio. THEY MUST BE SET UP SO THEY ARE FORWARD BIASED. That will drop the voltage by 3 x 0.7 = 2.1V. The current rating will be 6A x 2strings = 12A. No heat sink required, and the diodes will get warm, but not hot.

Do you understand that a silicon diode that is forward biased (i.e., conducting) has a 0.7-V voltage drop? That is the nature of the beast. It has nothing to do with the the diode's peak-inverse-voltage rating or even the amp rating. It's an inherent, physical property of the P-N junction in the diode.

I think you are making this too hard.
Doug

:I do not find any diodes in AES catalog that rate at the numbers suggested here. It looks like the draw is about 7 amps and I need to cut 2 volts into the 6V radio. A customer insists he wants to use the 8.42 battery in his 6v car. Radio Shack has 5 volt diodes but nothing less. Thanks.
:
:
:ALL garden-variety silicon diodes have a 0.7V forward voltage drop. Diodes, forward biased, are often used for DC voltage supplies.
::
::You don't need fancy diodes, like FREDs, etc. - just garden-variety silicon diodes.
::
::You could get a 6-V zener, and put that in series between the 8-V battery and the radio. But you still need to size the zener to handle the maximum wattage dissipation in the diode.
::
::The radio's fuse size might not be indicative of the normal current to the radio? Maybe by inspecting the schematic you can guesstimate the current draw?
::
::Is this a 6-V radio? Then you could hook it up temporarily to a 6-V supply, and measure the current draw with your DMM. You can use three or more "sacrificial" silicon diodes in series with the 8-V battery for testing.
::
::By the way, how come you are using an 8-V battery?
::
::Heat sinks aren't available for many diode packages. The power dissipation will be 0.7V times whatever the forward current is. You need to buy diodes that can handle the current.
::
::You may need beefier diodes, and put them in parallel?
::
::Homework time. Google is your friend, along with whatever books you have.
::Doug
::
:::Radio uses a 14 amp fuse as per schematic. Do I need a heat sink? I cannot find .7v diodes.
:::
::::Del: String three silicon diodes in series - each one drops 0.7V. Total cost less than $1. And they don't get hot like a resistor.
::::
::::What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
::::Doug
::::
::::
:::::I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

Thank you very , very much. Del

:Del, RadioShack (and other places, I'm sure) has just what you need: http://www.radioshack.com/product/index.jsp?productId=2062591&cp=&sr=1&origkw=diode&kw=diode&parentPage=search
:
:6-A diodes - four for $2.49. Put three pairs in parallel, then put those in series. You put the parallel/series string in the circuit between the battery and the radio. THEY MUST BE SET UP SO THEY ARE FORWARD BIASED. That will drop the voltage by 3 x 0.7 = 2.1V. The current rating will be 6A x 2strings = 12A. No heat sink required, and the diodes will get warm, but not hot.
:
:Do you understand that a silicon diode that is forward biased (i.e., conducting) has a 0.7-V voltage drop? That is the nature of the beast. It has nothing to do with the the diode's peak-inverse-voltage rating or even the amp rating. It's an inherent, physical property of the P-N junction in the diode.
:
:I think you are making this too hard.
:Doug
:
:
::I do not find any diodes in AES catalog that rate at the numbers suggested here. It looks like the draw is about 7 amps and I need to cut 2 volts into the 6V radio. A customer insists he wants to use the 8.42 battery in his 6v car. Radio Shack has 5 volt diodes but nothing less. Thanks.
::
::
::ALL garden-variety silicon diodes have a 0.7V forward voltage drop. Diodes, forward biased, are often used for DC voltage supplies.
:::
:::You don't need fancy diodes, like FREDs, etc. - just garden-variety silicon diodes.
:::
:::You could get a 6-V zener, and put that in series between the 8-V battery and the radio. But you still need to size the zener to handle the maximum wattage dissipation in the diode.
:::
:::The radio's fuse size might not be indicative of the normal current to the radio? Maybe by inspecting the schematic you can guesstimate the current draw?
:::
:::Is this a 6-V radio? Then you could hook it up temporarily to a 6-V supply, and measure the current draw with your DMM. You can use three or more "sacrificial" silicon diodes in series with the 8-V battery for testing.
:::
:::By the way, how come you are using an 8-V battery?
:::
:::Heat sinks aren't available for many diode packages. The power dissipation will be 0.7V times whatever the forward current is. You need to buy diodes that can handle the current.
:::
:::You may need beefier diodes, and put them in parallel?
:::
:::Homework time. Google is your friend, along with whatever books you have.
:::Doug
:::
::::Radio uses a 14 amp fuse as per schematic. Do I need a heat sink? I cannot find .7v diodes.
::::
:::::Del: String three silicon diodes in series - each one drops 0.7V. Total cost less than $1. And they don't get hot like a resistor.
:::::
:::::What is the current required? That will determine what diodes. 1N400x are good for up to 1A, only. 1N5408 handles 3A.
:::::Doug
:::::
:::::
::::::I still need to find the parts to make a 2 volt DC reducer to run a radio in an old car using 8 volt battery. Thanks.

73's de Edd

anks.