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Author Topic: Unicord Stage 65b Output Transistors  (Read 722 times)

Sfmag1

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Unicord Stage 65b Output Transistors
« on: April 29, 2019, 02:00:22 AM »
Hello. I have been working on a Unicord "Stage" 65b amplifier and ordered and installed replacement output transistors Sanyo B507E and D313E. They work alright with a signal from a generator or guitar at very low volume but  heat up and will burn/short out completely if left on with a louder volume setting. The sound is good out of an 8 ohm speaker until it is turned up, then they heat up. They would be normally mounted to the chassis to dissipate heat but they are burning hot anyway. The speaker reads ok at 8 ohms. I am suspecting the Chinese transistors I bought from e-bay are cheap junk and that is the problem. Any experience or advice on this? Should I buy an equivalent?
Tx

phatt

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Re: Unicord Stage 65b Output Transistors
« Reply #1 on: April 29, 2019, 03:44:36 AM »
Hello. I have been working on a Unicord "Stage" 65b amplifier and ordered and installed replacement output transistors Sanyo B507E and D313E. They work alright with a signal from a generator or guitar at very low volume but  heat up and will burn/short out completely if left on with a louder volume setting. The sound is good out of an 8 ohm speaker until it is turned up, then they heat up. They would be normally mounted to the chassis to dissipate heat but they are burning hot anyway. The speaker reads ok at 8 ohms. I am suspecting the Chinese transistors I bought from e-bay are cheap junk and that is the problem. Any experience or advice on this? Should I buy an equivalent?
Tx

ARRRRH,,  :o  Stop!!!  :o They have to be mounted BEFORE you turn on anything.
That is why the heat sink is there,, they cannot work without a heat sink.
Phil.

Enzo

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Re: Unicord Stage 65b Output Transistors
« Reply #2 on: April 29, 2019, 07:45:03 PM »
Agree^^^

ALWAYS put the power transistors on the heatsink before powering up.


How long would you run your car engine with zero water in it?  Or with zero oil in it?

Sfmag1

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Re: Unicord Stage 65b Output Transistors
« Reply #3 on: April 30, 2019, 06:49:58 PM »
Ok noted and will try. ??? 
« Last Edit: April 30, 2019, 07:01:32 PM by Sfmag1 »

Sfmag1

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Re: Unicord Stage 65b Output Transistors
« Reply #4 on: June 09, 2019, 04:38:01 AM »
Ok mounted to chassis and so far so good. :dbtu:

joecool85

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Re: Unicord Stage 65b Output Transistors
« Reply #5 on: June 13, 2019, 12:45:09 PM »
Ok mounted to chassis and so far so good. :dbtu:

Glad to hear it!  :tu:
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
thatraymond.com

 

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