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Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?

157.52.15.143
Posted on January 12, 2017 at 14:52:06
Paul Kehayas
Audiophile

Posts: 70
Location: Ontario
Joined: May 15, 2014
 I sold a Mcshaned Jolida 302B that I used to own to a friend of mine and now his is blowing fuses left, right and centre...they use fast blo fuses. Apparently he took the amp to the shop and they had it running fine for a few hours...everything was measuring fine.

The suggestion was initially that perhaps he was using fast blo fuses when he should have been using slow blo fuses....

I thought this probably was the main problem but now looking at the manual it does indeed state that for voltages between 110-120V the fuse to be used is a 6.3A fast blow.

What does everybody think - there are many dedicated threads to Jolidas blowing fuses....

Paul

 

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The shop "had it running fine"?, posted on January 12, 2017 at 15:12:20
Chip647
Audiophile

Posts: 2649
Location: The South
Joined: December 24, 2012
 Did you try a slow blow 4 amp fuse?

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 15:22:08
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Paul
When you say McShaned on the Jolida,that isn't the term we use on those.That term applies mostly to McIntosh amps,Citations,Eicos,and a few other vintage amps and preamps. The term applies mostly to Macs and Citation amps tho because of their circuitry and build of the power supply.
Now what you can say about the Jolida is an upgrade of McShane chosen parts which will be a definite improvement.
If he keeps blowing fuses,I would look for a bad tube,a leaky diode,or a bad solder connection on the board.Also,look for a bad solder connection on the power supply caps that may be arcing. Can you pull it apart and post a photo of the bottom side of the chassis where the solder traces are? You may have to have Emma remove the board.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 15:32:19
Paul Kehayas
Audiophile

Posts: 70
Location: Ontario
Joined: May 15, 2014
 Oops!

You are right! I shouldn't have stated that it was McShaned! Ok - he recommended and sent parts for this amp (made it even better!)

The amp is at the shop still because the volume pot and the selector switch was dirty (Jim recommended bypassing the balance control so that isn't in the circuit anymore)..

I can't take pics because of that fact. It's just that i brought this up here because I am head scratching about this one. They had it running for about 6 hours and tested it. Your suggestion that it was perhaps best to use a slow blow fuse mirrored the shop's opinion.

I was going to the local shop I was telling you about to purchase the MG Chemicals contact cleaner tomorrow and they had fuses (thought I should stock up and also to check what the Jolida manual states) and after reading the manual I found out they put fast blow fuses in the thing.

That's when I became a bit confused!


Paul

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 16:43:46
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002
 fast blow fuses are just normal fuses. Not to be confused with slow blo fuses.


If the fuse is blowing at turn on, did the upgrade include larger value power supply capacitors vs. the original capacitors?



Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 17:06:22
Paul Kehayas
Audiophile

Posts: 70
Location: Ontario
Joined: May 15, 2014
 This is what was done to it when we modded it - these are Jim's words I am copying and pasting here...

1. replace the R17 & 18 1 Ohm 5 watt(!) resistors with
1 Ohm 1 or 2 watt.

2. Remove the 220uf/300 volt C6 & C7, replace with 680uf/250 volt
Panasonic ED. Save the 220/300, we'll reuse them.

3. Add (3) missing bypass caps, use .68uf GE MPP caps
(if the board doesn't have holes for them don't do it).

4. Replace C8 & C9 470/400 with 220/300 just removed

4a. (Option) Add .15 mh choke from in series with each B+
feed to the output transformers. If you don't add these chokes
leave the 470/400 caps in place

5. Replace stock diodes with UF5408 fast Vishay diodes

6. Replace the bias diode VD5 with a GI 856 fast/soft diode.

7. Replace R13 & R16 with 10K (or 1K if originally equipped)
carbon composition resistors

8. Replace the coupling caps - use .47uf/600 volt Rel-Cap
PPFX for C1 and .22uf/400volt K40 PIO (body insulated
from PC board) for C3 and C4.

Paul

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 18:06:51
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Paul
If you did all that,that would be a McShane and I'm sure it made a hell of an improvement.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 12, 2017 at 20:56:04
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002
 4. Replace C8 & C9 470/400 with 220/300 just removed

That would lower the turn on surge current, not increase it.

Does the fuse blow at turn on?


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 13, 2017 at 05:03:35
Paul Kehayas
Audiophile

Posts: 70
Location: Ontario
Joined: May 15, 2014
 It's done it at turn on and also within anhour. All new tubes in the thing too. They tested fine.
Paul

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 13, 2017 at 07:50:57
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002
 There has to be a leaky cap somewhere.

I would look at the caps that used to be C6-C7 that are now in the C8-C9 position.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 13, 2017 at 09:50:41
Jim McShane
Dealer

Posts: 5910
Location: Chicago
Joined: January 13, 2003
 I sent the parts to Paul in January of 2009 - so the now 8 year old caps that were installed then should be fine. But the relocated 220 uf caps are getting a bit long in the tooth so I agree with Tre. They could be acting up.

It might be wise to replace them just as a matter of course after all the years of service.

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 14, 2017 at 08:57:26
Jonesy
Audiophile

Posts: 3156
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since: March 1, 2018
 Was this a recent sale to your friend or had he had it for some time before the issue showed up?

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 14, 2017 at 11:10:47
Paul Kehayas
Audiophile

Posts: 70
Location: Ontario
Joined: May 15, 2014
 It was sold to him around 2012. He has done nothing to it. No mods or changes.
Paul

 

RE: Friend's Jolida 302B blowing fuses....why do they use fast blo fuses in this thing?!?, posted on January 14, 2017 at 11:34:31
Jonesy
Audiophile

Posts: 3156
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since: March 1, 2018
 Ah. He's had it for quite awhile. I thought perhaps it was recent and not adapting to speakers or cables in his system.

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

RE:If during the rebuild CLs were installed then fast blo fuse is ok., posted on January 14, 2017 at 22:33:08
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 The current limiter would supercede the need for a slo blo fuse. If none were installed you should consider putting them in.

 

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