Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Jun Mon 17, 2019 12:30 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 46 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: Tube push pull amplifier question
PostPosted: Nov Thu 24, 2016 7:02 pm 
Member
User avatar

Joined: May Tue 26, 2015 10:12 am
Posts: 170
Although I don't have this amplifier, the discussion and procedures have been educational.

How does the amp sound, with what speakers you use, and what input gear?

Regards. -BMS-


Top
 Profile  
 
 Post subject: Re: Tube push pull amplifier question
PostPosted: Nov Thu 24, 2016 8:38 pm 
New Member

Joined: Nov Tue 01, 2016 7:33 pm
Posts: 23
Sound awesome!Great punch!
Speakers could be better; Spkr #1 Technics A51 and #2 vint Fishers. Inputs, again nothing fancy; Finely tuned multiplex
integrated tuner, and Sony dig player CE500, beyond my ears capability. Thanks Martin


Top
 Profile  
 
 Post subject: Re: Tube push pull amplifier question
PostPosted: Apr Wed 19, 2017 11:07 pm 
New Member

Joined: Nov Tue 01, 2016 7:33 pm
Posts: 23
Another question for tube amp aficionados and Radiomania: Same model Fisher 500c different unit: This time is about the bias supply: I aim to have -19 vdc bias adjusting R-132 to aprox 2.5 K as suggested by Fisher Doc, usually not a problem; but in this case I can barely reach -19 vdc reducing R-132 to 100 ohm ! What is worse, I get a ripple of 7 vac.
I have replaced bridge twice, new tested electrol 1000uf x2, main transformer replaced ( for other reasons). No change when removing pwr tubes. The only defect known is a faulty OPT (one leg) waiting for replacement.
Any ideas are very welcomed.. Thanks Martin


Top
 Profile  
 
 Post subject: Re: Tube push pull amplifier question
PostPosted: Jun Sun 25, 2017 11:16 pm 
Member

Joined: Apr Tue 30, 2013 11:03 pm
Posts: 578
Location: Tioga, TX
If I understood correctly you replaced the two 500-C output transformers with model 400 transformers. That being the case, have you looked closely at the values used in the negative feedback loop between the two designs? I would suggest that you install the same R/C values used in the model 400 schematic of the serial number sequence model 400 that you took them from. Over time I believe the model 400 output transformer part numbers changed and they were not the same. So look at the appropriate SN sequence model 400 schematic and duplicate the negative feedback RC values that were used in the chassis these transformers came from. The model 400 schematic I looked at showed a 330pFd cap from the 16 ohm tap to chassis ground in the negative feedback loop. Other serial number sequences in the model 400 may be different. Compare against the values originally used in the serial number sequence of the 500-C model you have. Also compare any differences at the driver/phase inverter stages. Those may suggest possible changes to try and see what impact they have on performance and stability of the combined stages.

Joe


Top
 Profile  
 
 Post subject: Re: Tube push pull amplifier question
PostPosted: Jun Mon 26, 2017 1:36 pm 
New Member

Joined: Nov Tue 01, 2016 7:33 pm
Posts: 23
Thank you Joeatech: Good advice. I have not checked that, and I dont have this unit anymore. It would be an interesting procedure which I will do, should the same
situation occurs . Martin


Top
 Profile  
 
 Post subject: Re: Tube push pull amplifier question
PostPosted: Jul Wed 25, 2018 9:05 pm 
New Member

Joined: Jul Wed 25, 2018 8:57 pm
Posts: 1
Radiotechnician (Steve Dow),

I saw a posting you had on the Antique Radio Forum whereby you posted a couple jpg's from IHF-A-201.
I having been looking all over for a copy of IHF-A-201. Is there some way I could obtain a copy from you?

Thanks!
Ed


Top
 Profile  
 
Post New Topic Post Reply  [ 46 posts ]  Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB