> Trying to repair Amp and understand how the thermal cutout works.
>
> The circuit employs a thermal switch that is N.O.
>
> It is connected to the base of an NPN and PNP in series.
>
> Attached is image of a circuit that hopefully captures the essence of the
> real circuit. I hope that I have not missed anything too important.
>
> I have tried to analyse in LTspice but the voltage levels around the
> circuit remain unchanged regardless of the state of the switch.
>
> I assume the idea is that the balanced input signal is clamped when the
> thermal switch closes.
>
> Hoping someone may be familiar with this approach and help explain how it
> is intended to work.
>
> Justin
>

> I have confirmed with both the schematic and the actual amp that the
> collectors are tied to the bases and both transistors bases are tied to
> each other,.
>
> It remains a mystery and considering that they are used in some way to
> provide diode volt drops that match another pair of the same transistors
> that are closely bonded on the same heat sink.
>
> I would like to make the manufacturers schematic available but I have been
> asked not to do so.
>
> Justin
>
> On 5 September 2016 at 11:08, RussellMc <apptechnzspam_OUTgmail.com> wrote:
>
>> Are collectors really joined to bases, as shown?
>> --
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>> mailman.mit.edu/mailman/listinfo/piclist
>>
>
>

> in previous post
>
> "..and considering ..".
>
> should read
>
> "...and I am considering ..."
>
>
> Is it possible that they are temperature compensated biasing.  Still not
> 100% happy as does not explain how the thermal shutdown works.
>
>
> Justin
>
> On 5 September 2016 at 15:42, Justin Richards <KILLspamjustin.richardsKILLspamgmail.com>
> wrote:
>
>> I have confirmed with both the schematic and the actual amp that the
>> collectors are tied to the bases and both transistors bases are tied to
>> each other,.
>>
>> It remains a mystery and considering that they are used in some way to
>> provide diode volt drops that match another pair of the same transistors
>> that are closely bonded on the same heat sink.
>>
>> I would like to make the manufacturers schematic available but I have
>> been asked not to do so.
>>
>> Justin
>>
>> On 5 September 2016 at 11:08, RussellMc <RemoveMEapptechnzTakeThisOuTgmail.com> wrote:
>>
>>> Are collectors really joined to bases, as shown?
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> mailman.mit.edu/mailman/listinfo/piclist
>>>
>>
>>
>