Ampeg V4.com

greengoblin · 2013-05-31 22:13:11

Right now I am working on my personal early '70's v4b. Pots date to '70 and the chassis is a Linden, NJ flavor. Doing the regular maintenance (caps), testing, some upgrades I have found like the 1k5w screens, individual components on the tone circuit instead of the one piece unit (thanks Hangman!)..... Soon will do adjustable bias (have the parts) and already picked up some 6550's as I like the deeper tone they produce over the 7027's. (at least to my ears)...

Since I plan on keeping this amp I spend a lot of my free time on it beyond normal testing and replacing. Replacing jacks and a few pots just because I have them in stock and these are old.

One thing I noticed over some of the later 70's v4's I have owned is some of the wiring is very small. Maybe 22gauge or smaller. Any thoughts on if this should be replaced with a thicker gauge, or is the general concensus to leave it be unless there is an issue?

Also, I have replaced all of the caps in the head, even on the boards. What about resistors. As long as it is in spec leave it be, or since I will test things, replace it since it is close to 43 years old?

Last, but not least.. Having a hard time find the part numbers on the Diodes.Specs on on the schems for D1-6....

**EDIT** Found that the 1-5 diodes can be swapped with 1N4007's, which I have... D6 Looks like it may be a 3A or 1N5408.

Thanks!

Last edited by greengoblin (2013-05-31 22:32:15)

greengoblin · 2013-05-31 22:15:48

One added note. Something I thought was weird on this head is even though it is a v4b, I have a .033 cap in C22. Although this cap does not show for a v4b.. Only for V4 heads on the schems..

hangman · 2013-06-02 02:49:28

I see c22 as part of the ultra low circuit in the v4b.

It's on the schematic we have posted for the 1971 v4b.

greengoblin · 2013-06-02 15:20:49

Thanks Hangman... Not sure how I missed that one, guess I needed o take a break.. Lol worked on my brother bassman project all day and then this the rest of the day.. Too many schemes!

What is your feeling on the wire? Do you leave yours alone unless there is an issue?

hangman · 2013-06-03 01:21:01

The wire is a little thin compared with some manufacturers, and solid core too. I've never thought it was a big enough issue to replace all of the wiring. We are talking about pretty short runs. I think if I was building a v4 myself, I would have used thicker wire, but I can't imaging it would make much of a difference if any in sound.

greengoblin · 2013-06-03 16:45:46

Well I'll let you know... I haven't had much time on this amp so I won't have a good A/B comparison...

From working on Fenders a lot, I ran new wire for the heaters, some grounds and all new wire for the caps.. Used 18ga solid as it is what I had on hand... Thought I hand 20ga, but on hand 22stranded, so any wire with melted insulation I am replacing.. We will see...

The purists probably won't like it... But I have gutted some rare Fenders too per requests..

hangman · 2013-06-03 21:30:03

I consider myself a moderate purist, but I wouldn't gut any vintage fender, Marshall, hiwatt ampeg or other, except for a Dukane, Bogan or other old tube PA head. There is no good reason for it.

Usually a customer asks me to make their 60s fender sound like a Marshall, and I tell them to sell their fender and get a Marshall.

greengoblin · 2013-06-04 05:07:38

Well it is nice to keep some pure. Picked up a 66 bf bassman with an aa165 circuit as he had a 65 he wanted to keep stock. He was after that Mike Ness tone so I cleared the board and started over.

I am keeping my early v4b to the schem specs, just refreshing the internals.. Only changes are adjustable bias and 6550's. Oh and the discreet components in the tone circuit!!

Glad I started redoing some wires as I've found some loose connections..

Last edited by greengoblin (2013-06-04 05:10:38)

hangman · 2013-06-04 20:23:31

greengoblin wrote:
Well it is nice to keep some pure. Picked up a 66 bf bassman with an aa165 circuit as he had a 65 he wanted to keep stock. He was after that Mike Ness tone so I cleared the board and started over.

...yikes

greengoblin · 2013-06-07 22:40:41

Well they say if it isnt broken, dont fix it. I know I should always listen to this....... haha

Carefully went through a cap job and followed the schem and replaced resistors. All one at a time, pull it, verify its value, install. Did this with caps and resistors. Also did wires for the filter caps and replaced all jacks.

Before replacing anything, the amp was working great. Afterwards, not so great. It is a PCB board so it is not so easy to mis-wire. Went back through everything and made sure everything was installed as it should have been.. It would power on fine, but as soon as it came off standby there would be a constant thumping through the speaker.
I could pull V1-V3 and none affected the thump.Pulled the 6k11 and still the same. If the 12au7 and power tubes were installed it always thumped off of standby.

All voltages test as it should with power tubes pulled.. Some were off by no more than 10volts on the preamp tubes, but was getting 540v on the power tubes and 6.3v on the heaters. Only voltage that was not close was pin # 6 on the 12au7 as this was 334v rather than 200.. The 47K resistor tested fine and replaced it with another tested 47k resistor and it was not dropping the volts.

Online I have read of suggestions of a bad cap... Replaced a few on V4 to test, no change. Ened up within a few caps on the main (long) board and just replaced them all.. Stupid move, but I had the time. No difference.

Started analyzing the whole amp and wiring. Was there anything I mis-wired or made a mistake..??.. Found on the lower output jack where there is a ground wire and the brown ire from the Ext jack loop through the two lugs on the output. I had the lug configuration reversed on these. Rewired and quadruple checked it was good (wiring wise)...

Tested her again and and I got an arc on V5 from pin 2 to pin 3, then it blew a fuse. These areas "looked" clean to the naked eye.. So I scrape the suface with a screwdriver and cleaned with rubbing alcohol.

Found on here about using higher rated diodes and a similar situation of a possible diode issue. So I replaced all 1n4007's (D1-5) with 1N4508's.

Now I get a clicking, slight squeal in the power tubes with a blue glow when coming off standby. Immediately shut her down...

I know I should've just buttoned her up when I had the filter caps done and she was purring like a kitten..

greengoblin · 2013-06-07 22:54:59

An added note. The only preamp wires I ran new wire for was from the heaters on v5 to the many where they connect near the V4 socket. Yellow to V5 pin two, blue (i used green) from pin 7. On the board it conencts on each side of the "V4" designation. Yellow next to the V, green (blue) next to the 4....
From pics online, they show that I wired them correctly...

The other was two wires from the small PCB at V201 to the large PCB at tube socket V1. (used yellow and green) Yellow is on the "V" side of V1. Green is on the "1" side. On the small PCB, Yellow is just above Pin 12 on V201 and Green is just above Pin 1....

Just thought I would point it out. I am sick to my stomach that somehow I mis-wired something and afraid I caused an issue because of this.....

greengoblin · 2013-06-08 13:33:37

Pic links:

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

hangman · 2013-06-09 01:04:57

dude, you gotta be careful with this stuff. you can't just replace a bunch of stuff without paying attention. frankly your work is sloppy and mostly unnecessary. Don't be another guy that does bad work, there are too many of those already. think: Balance. fix what is in need of fixing, don't go crazy and throw brand new everything in there. That is a mark of a Tech that doesn't know what they are doing.

your filter caps... what is going on there? it looks like when you rewired it you put C20 where c18 was and vice-versa. but you attached the center tap of the output transformer (the orange wire) to the negative end of C19? halfway between the screen filters. (which would have been the positive terminal of C20 had you left it the way it was.)

the work needs to be done more cleanly, you should have followed ampeg's layout.
I could recap a V4 with my eyes closed, but it took a bit to make sense of the work you did. it shouldn't be that way. it should look just like any other V4 that I look inside.

greengoblin · 2013-06-09 18:19:05

I should have prefaced the pics to note the upgraded wiring is a mess right now from tracing. It was all neat and it order. I don't have the head in front of me, but will double check when I am home. The 3/4/5 power tube wires were the same as when I picked up the head and haven't been touched.

The + off the 40uf cap is going to B on the board. The red wire from the tranny is going to C and the orange center tap to D.. Notes these the night before when tracing items..

I normally wouldn't replace everything in a head unless rebuilding a circuit on a say a ptp board. Got this as a non-working project head. Had it up and running and wanted to try it this way since it was own personal project and had it running wire before upgrading the wiring.

hangman · 2013-06-09 18:51:58

The red wire you mention must be going to the filter caps in the back corner. Not the transformer. But your orange wire that IS going to the output transformer Is connected to the wrong spot.
The orange wire isnt connected to D right now, and even if it was it should be connected to A.

Do you see what I am sayin?

greengoblin · 2013-06-14 00:12:52

Had a few mins to research some of my pics with other ont the board and think I found my mis-wire.. Have friends in town so won't be able to work on it til late Sunday probably. Will report back with my findings.. (Think I wired the Ot ct to the wrong cap term)

Btw, does a '70 v4b schem exist? All i can find is a v4 1970 schem and a '71 v4b.. My head does not have c23 as shown in the 1971schem (c15 is a 100uf/100v cap) and not sure if there are any other differences. Googled and searched, but came up empty so far..

And thank you (as always) for the replies so far hangman! It's nice to have people to talk with about issues!

greengoblin · 2013-06-16 23:33:12

Ok, had some time to work on the head. Had a couple wires mixed ont he filters. Have those Straightened out now. Not sure how it happened.

One last wire I am tracing and cant find reference or pics online as to where it should go, just double checking. Included a pic link below:

https://docs.google.com/file/d/0BxnnMX7 … sp=sharing

Thanks!

greengoblin · 2013-06-17 01:55:23

On the power tubes, Voltages are (no tubes):

Pin 3 & 4 for all four tubes 538

Pin 5 on all four tubes jumps around on my DMM without giving a steady measurement.....

hangman · 2013-06-17 02:09:36

Pin 5 should be your bias voltage. Do you measure continuity from the bias cap ground to chassis ground?

greengoblin · 2013-06-17 03:49:59

Hey Steve, thank you for the reply!

Please excuse me if I performed this wrong, but I connected my DMM from the "-" side of C15 to chassis ground and I am not getting a voltage reading.

I replaced the 12au7 and the 3/4 voltages went up to 553. Also, I pulled R49 to test it's resistance and it measured 74.4k. I replaced it witht he trim pot I planned on using for the adjustable bias and it is set at 90.5k currently.

New measurements on the power tubes for pin 5:

V5 and V6 the voltage reading still is not steady. DMM jumps all around.

On V7 and V8 Pin reads 3.61 VDC...

hangman · 2013-06-17 07:47:53

The bias supply is a negative voltage. Meaning that the voltage is negative with respect to ground. Conversely, ground is positive with respect to the bias supply voltage.
So the negative "-" end of c15 is not ground, it is the supply end. The "+" side of c15 is ground.

Does that make sense?

greengoblin · 2013-06-17 19:55:21

I am not getting any voltage readings on either side of C15 when connecting to it and the bolt next to the tranny. Also used the ground at the board, still no voltage.

Strange I get positive voltage on one side of the power tubes and weird readings on the other....

I messed up the wiring on the multi-caps next to the power tubes originally. Had the OT CT on the wrong terminal. Did this on my other V4 recap job and thought I learned, but that was 2 years ago..
Got that squared away according thanks to this pic: http://i281.photobucket.com/albums/kk21 … wiring.jpg

I put the heaters back to 22ga stranded just because I wasn't thrilled with the way the 18ga turned out and was in the way.

The other wires I replaced with 18 ga are the multi-caps.
The multicap in the rear corner near the imped switch are:
Triangle to D
Square to C
Half Circle to B

There was a second yellow wire coming off of triangle and it went to the small PCB board between C201 and the corner bolt.

Center tap is going to one positive leg of the 50/50 cap as well as red from "A". That positive terminal is jumped to the other 50uf term as per the diagram. The 100/100 is wired the same as well. Ran new wire for the brown wire to correct terminal on these caps.

There is a black wire from between C15 and R55, runs to pin 8 on V6.

Ran new 22ga heater wires for V201 to V1. On V201 green (was blue I think) goes to pin 1 (hole in the board with trace to pin 1) yellow to pin 12. V1 green goes to pin 1, yellow goes to pin 9...

Ran new heater wire from V5 to below V4. V5 yellow is on pin 2, green (was blue I think) on pin 7. below V4 yellow is near the "V", green is after the "4" in a hole near pin 6 of V4. Traces look like the run down the board and not directly to V4.

All preamp and rest of the power tubes are original wires. Will get voltages for all tubes soon. Something is definitely not correct in the bias section for the readings I am seeing. All diodes are new as well... But I have more if pulling and testing would be best.

Hope I am not over loading you with info.

greengoblin · 2013-06-17 20:01:41

Voltage at A is 538, B is 538, C is 455 and D is 369.

All voltages are in line with Rytetones voltage postings on his page with the exception of V3.. I am getting a positive volt reading on Pin 2 with 90.5 volts. This should read 0. Tried two different 12dw7's...

Going to pull and measure R16 and r18 as well as C8....

hangman · 2013-06-17 20:29:07

Slow down.

What I am asking you to do is very simple. The amp shouldn't be on to do what I am asking you to do.

Turn your multi-meter to continuity test.
Then put one terminal to ground, the other to the positive terminal of c15. The meter should beep at you or buzz if it is a short.

All we are testing is if your bias supply is referenced to ground.

Who told you pin 2 of v3 should be zero? It shouldn't be zero

greengoblin · 2013-06-17 23:59:30

Sorry, got some bad news earlier and oddly enough this stuff calms me and takes my mind off things. I had the time and tried giving you as much info as possible.

Did the continuity test and did not get a beep.

**Correction** Re-tested and received an audible beep..

Looks like D6 may be shorted as well. Both sides of the test show a small voltage. All other test with one side OL and a small voltage around .475 on the other side.

Last edited by greengoblin (2013-06-18 03:37:34)

Ampeg V4.com

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#1 2013-05-31 22:13:11

Early v4b upgrades and wire?

#2 2013-05-31 22:15:48

Re: Early v4b upgrades and wire?

#3 2013-06-02 02:49:28

Re: Early v4b upgrades and wire?

#4 2013-06-02 15:20:49

Re: Early v4b upgrades and wire?

#5 2013-06-03 01:21:01

Re: Early v4b upgrades and wire?

#6 2013-06-03 16:45:46

Re: Early v4b upgrades and wire?

#7 2013-06-03 21:30:03

Re: Early v4b upgrades and wire?

#8 2013-06-04 05:07:38

Re: Early v4b upgrades and wire?

#9 2013-06-04 20:23:31

Re: Early v4b upgrades and wire?

greengoblin wrote:

#10 2013-06-07 22:40:41

Re: Early v4b upgrades and wire?

#11 2013-06-07 22:54:59

Re: Early v4b upgrades and wire?

#12 2013-06-08 13:33:37

Re: Early v4b upgrades and wire?

#13 2013-06-09 01:04:57

Re: Early v4b upgrades and wire?

#14 2013-06-09 18:19:05

Re: Early v4b upgrades and wire?

#15 2013-06-09 18:51:58

Re: Early v4b upgrades and wire?

#16 2013-06-14 00:12:52

Re: Early v4b upgrades and wire?

#17 2013-06-16 23:33:12

Re: Early v4b upgrades and wire?

#18 2013-06-17 01:55:23

Re: Early v4b upgrades and wire?

#19 2013-06-17 02:09:36

Re: Early v4b upgrades and wire?

#20 2013-06-17 03:49:59

Re: Early v4b upgrades and wire?

#21 2013-06-17 07:47:53

Re: Early v4b upgrades and wire?

#22 2013-06-17 19:55:21

Re: Early v4b upgrades and wire?

#23 2013-06-17 20:01:41

Re: Early v4b upgrades and wire?

#24 2013-06-17 20:29:07

Re: Early v4b upgrades and wire?

#25 2013-06-17 23:59:30

Re: Early v4b upgrades and wire?

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